What time do you put her down now?
My 4yr old and 2 yr old still have a day sleep - but I found when they hit 2 I had to adjust there day sleep. If you put them down to early (between 9am - 11) then they won't go down or sleep for very long, if you put them down too late (3pm - onwards) then they stay up till all hours at night.
I try and wear my munchkins out in the morning, give them some lunch and pop them down at about 12.30 - which is around the same time they go down at daycare - 95% of the time it works too and they have a good sleep sometimes till 3 - and 12.30 onwards seems to be the quietest part of the day. If they are quite wound up, I pop them on their bed to watch a movie and they are out to it within 20 minutes.
Hope this helps?