Get a routine and stick to it. Sleep is very important to developing kids and should never be compromised. At 2 1/2 years old she should be getting an average of 12 hours of sleep a day - all at once or including naps.
Be firm. Dinner, bath, book, bed. No ifs, ands, or buts! If she puts up a fight, ignore it - do not fuel it. If she gets out of bed return her to bed without converstaion. This will take some time but once you get it it will be awesome.
Supernanny demonstrates this method well. I do not know if it is still on TV but try and see it if you can.
Good luck.
A.