I would still offer the nap; however, she may only play for an hour or so in bed. She needs some quite time still at this age and most likely will fall asleep eventually. I have a 2 1/2 year old and on occassion my daughter will go through the day without taking a nap. She will just sit in bed for two hours and never fall asleep. I put books on her end table. Also, you may want to make sure she is getting enough excerise - playing outside, using her mind, etc. I notice when my daughter has a very active day she is more inclined to nap easily which is good for her brain as well. However, I would say about 99% the time she falls asleep. Probably just a phase.
Good luck!