I have found the "SuperNanny technique" of NOT talking or engaging them in any way, and repeated walking them back into their room. I don't know who told you to put her in timeout everytime she comes out of her room, however that sounds to me like it IS engaging her - giving her attention for not behaving...even if it is negative attention, she's ultimately getting what she wants. Your attention.
I have tried this "technique" myself and can say with absolute confidence it works.
When you put her to bed for the night, tell her as you tuck her in, "Good night. I love you. I'll see you in the morning." The first time she comes out of her room, don't yell, don't get worked up. Just get up, walk her back into her room. Tuck her in and say, "It's time to go to bed now. Goodnight." The second time she comes out of her room NO TALKING. Simply walk her back into her room. If she puts up a fuss/fight DO NOT TALK TO HER, just pick her up and take her back into her room. Do this over and over and over again...No talking, no consoling, no punishing, just put her in the bed and walk out. If she doesn't get your attention she WILL eventually give up. Keep doing this every night - don't change the process.
I am sorry I don't have a simple, quick answer. I think she's doing this just to get your attention and because she knows how to push your buttons.
After doing this technique, my children have learned, "Mom says goodnight and THAT'S IT." I have explained to my children that they get PLENTY of hugs and kisses during the day and that bedtime or after bedtime is not the time to be asking for more attention. (They are 6 and 4 now.)
We have a bedtime routine which helps eliminate the "attention" they need. They get their cups for their night tables, get changed, go pee, brush teeth and we read stories. They get hugs, kisses and tucked in. I say, "Good night. I love you. See you in the morning." Period. We're done.
I think the overall keys to having your kids listen to you are:
1) start young - which you already are
2) mean what you say - don't threaten, use logical consequences
3) use incentives for good behavior and logical consequences for bad.
4) incentives and consequences are immediate - not "when we get home" - embarrassment in front of friends, family, etc. is part of the deal. They act up, you deal with it immediately, even if it means leaving a grocery store cart full or leaving a playdate
You are going through a very stressful time right now. Give yourself a break. If you can create ANY "me" time, you'll be a better mom because you won't feel so stressed out and get frustrated so easily. Just try to remember that you are the adult - so if all else fails, give them a timeout and cool off before you react.
Let us know how it goes.
Sara