Why the Change in Sleeping Habits??

She's at the age where fear can take place. DO YOU like sleeping alone in the complete dark, door closed and no one next to you in bed? I'll chance that it's a no. If an adult doesn't want to be like that, why would you expect a very small child to be?

Let her have her night light and door open. Put a gate up if you feel she may leave her room. Also,. move back bedtime 30 minutes so her normal time stays the same even if she adds 30 minutes to it. Be patient with her... she's a toddler!

I agree with pamela, raven, and son... I don't like the door shut and I actually sleep with the bathroom light on. She is at that age where she's developing fear and is scared of the dark. I actually shuddered that she slept with a door closed for a year... to me that's scary.. I feel trapped and vulnerable when a door is closed like that, I bet she is starting to with the way she is acting. Have you put a night light (or bathroom light on) and keep her door open now? If not you need to or she will be like me, wanting a light on as an adult lmao. If she'll leave the room put a gate up, she will still feel not trapped because there's communication if she needs it and there's more openness than a shut door. My daughter is 2.5 and doesn't take a 3 hour nap and stopped but still needed one cuz she'd get grumpy. I started laying her down at 1145, turning on a plug-in fan, and would lay down with her but in my normal sleeping position facing the wall (she sleeps with me :D) and she'd go to sleep within 15-30 mins. She sounds like she was an easy child so lucky you, but now that she has fears and is changing (as children naturally do :P) you have to address them and transition yourself with her developing personality quirks.

-They tend to develop fears as they get older (possibly from the TV we watch). My son did the same thing at that age.
-I say delay her bedtime by 1/2 an hour. Try 8:30 first. If that doesn't work then 9pm. It will most likely go back to 8:30 later.
-She may not be as tired.
-Tire her more through out the day having her run, chase her (I know, I know you're already tired). :)
-Play active games: hide and seek, throw a ball
-Put a nightlight in. As I said, they change and develop fears. Where they may not have needed a nightlight before, now they do.
-Could you try not shutting her door for now? If you have pets and are afraid of having them wake her, put a baby gate across her doorway.
-You say she doesn't act tired during the day now so get her more active so she will be tired at night.

Because she is growing and changing. My kids were all done napping at two, though we still had quiet time for an hour every afternoon. They were also staying up later as they just weren't ready to fall asleep at their old bedtime.
Give her a clip on reading light for her bed so she can stay up "reading" while she falls asleep, she can even "read" to her stuffed animals :)

What causes it? She's two years old! A lot of changes seem to come at this age.
My solution for this is that you could allow a small night light in the room. They make cute character night lights or if you prefer something smaller you could get one of the LED lights that put just a dim glow in the room. I suggest that the light be placed where it would give a bit of light for the exit from the room.
It also doesn't hurt to leave the door open a crack if it reassures her while getting to sleep. Let her know that you will close it when you go to bed, so that she doesn't freak out if she wakes and finds it closed. Kids feel 'tricked' if we aren't up front with them about such things, and that can cause them to lose trust in us... not something we want them to do, for sure!
Talk with her during the day and just prior to bedtime about the potty situation. Let her know that it's ok to get up if she really has to go potty, but put a limit to it. I wouldn't try to limit how long she sits there the first time out, but let her know that one time getting up should be enough... and stick to that! It definitely sounds like she is playing you with the potty thing. Kids learn quickly what will trigger our sympathy response and they use it! Be firm but gently in enforcing the potty rule.
Finally, check to see if you may have too much going on in the rest of the house after putting her to bed. Turn off any unneccessary lights. Keep TV or other noises to a low volume. Talk quietly so she isn't hearing you "having fun" while she has to sleep.
You most likely are having to deal with the seven month old's needs after your two year old goes to bed. Imagine her lying there thinking "mom is still playing with the baby, but I'm in here all by myself". Anything you can do to help her not be as aware that activity is still going on in the house will help her to settle down and sleep. If it's possible for the rest of you to shut down all the rest of the house and go into your room and close the door, that might help too.

Wow does this sound familiar :)
Our 2 year old, well ok 3 on Monday, goes to bed around 9 or so, but she will be up in her room until 1030-11 most nights!
She doesn't freak out, but instead is in her bed "reading". We tried to take the books away and make her lay down, but later we decided that if she is not coming out of her room and she is happy, then why fight it and make it a battle.
She too there for awhile did the whole, I have to pee routine. That did suck big time, but we started to tell her she could get up and go on her own and then had to tuck herself back in. After about a week of us not giving her that potty attention, she gave up on it.
We did end up getting her a princess flash light for her bed. I found it at Lowes one day while checking out. It is small and hand held. Although it probably eggs on the reading at night, she was doing it in the dark anyhow, so we thought what the heck, lets help her see the darn books.
Perhaps your daughter would like a flashlight or something similar to help with her fear. I had a terrible fear of the dark, so I know how it feels... my mom too just left the light on for me :)
As for naps.... our girl will go 50/50. Half of the week she will sleep 2-3 hours and the rest of the week she won't nap at all. We just tell her on those days she still have to be in her room until a certain time and then she can come out. Basically when she hears her little sister get up, she knows she can come out. That works for me. I still get my quiet time and some times she does just fall asleep!
Good luck... you are not alone!

If you know bedtime is taking longer than it use to - plan for it and start bedtime routine earlier.

If she falls asleep in the car, she might still need a nap, whether she wants one or not. Kids who are overtired are harder to get to sleep at night. I would encourage napping, or at least quiet time.

I'm reading a book called "Nurtureshock" and one chapter talks about how even one less hour of sleep a day has a significant affect on children's brains.

I remember my daughter being challenging to get to nap at this age (well, at every age) but I stuck with it and she napped right up until Kindergarten.

My DD stopped napping at 2. After about the third day of not napping, I thought I would do the whole, "well dont nap and see where that gets ya" routine. She was absolutely fine and went to bed earlier.
Who knew?

I guess it IS like they say...all kids are different.

It sounds familiar to me too. My son is 2.5 and he was difficult to put down for a nap and taking forever to fall asleep at night. We are potty training and without fail, he insists he has to use the bathroom after we are finished with our night routine. And he would sit there all night if I let him. I think he likes the feeling of controlling when he pees. Anyway, what I do is let him pee, give him a minute, and then I say, "when I count to 3, we're going to flush the potty and put on your diaper." And then I do it. He used to get mad and I'd be calmly diapering him while he protested, but now he's resigned. For the napping, I continued to attempt it. If it took longer than half an hour, I'd give up. At least he had laid down and rested for the half hour even if he didn't fall asleep. He only sleeps for about an hour anyway so it seemed stupid to struggle about it. I wasn't sure if he was ready to give up naps, but eventually, he started napping again. We are in a phase right now where he's waking up at night or super early after sleeping through for quite a while now. I'm chalking it up to the potty training since it's a new skill and developing new skills seems to ravage the sleep around here. Not a very helpful response, but I just wanted you to know you're not alone!

My daughter went through several changes at that age too. She went from sleeping with the door closed to needing it open and having a night light. Naps started to become an issue too. I was able to hang on to them for a few more months but by 2 1/2 my daughter was done napping. I was so sad. As far as going potty after she is in bed try setting a timer. Give her 1 minute to sit and tell her when it goes off she is done.