I would do the opposite of whatever it is that Emily is trying to get from this behavior. If you tell her that it is bedtime and time to go to sleep, then even 'a little quiet playing' is disobedience. Make her (as much as possible) put the toys back where they belong - if she is big enough to pull the toys out, then she is big enough to put the back, and then put her back down.
Consider changing your bedtime routine so that she has the opportunity to go pee-pee every 10-15 minutes, maybe 3 times total and on the last time, tell her that this is the last time she can get up to go potty for the night, so she needs to really squeeze the pee-pee out.
Also, change how you respond to Emily in the middle of the night. I don't have any good ideas, but apply the principle of giving the child the opposite of what she hopes to gain from waking you up at 3 or 4 in the morning.
However you decide to manage Emily's sleeping, know that it is in her best interests to get a full night's sleep as well. Whatever you do it is in her best interests, even if she doesn't like it at the time. The middle of the night waking disrupts her sleeping pattern as well and has similar effects on her mood throughout the day as the effect it has on you.
At 28 months she is probably not physiologically able to stay dry throughout the night, but you can lower her afternoon liquid intake. Since she's actually able to produce urine every 15 minutes from 8:00-10:00 at night, then she's probably been drinking too much too close to bedtime.
As far as the nap, make whatever rule you have to, something like this is Mommy's and Emily's quiet time so you have to stay on your bed. You don't have to go to sleep, but you do have to be quiet and stay on the bed. Then every time she gets off the bed respond with whatever is your preferred discipline technique.
Good luck and congratulations on #2,
E.