Just saw this question today - We had the same problem - the best antidote is non-chemical, but time consuming. Someone has already mentioned - slightly different, though.
Mix conditioner with a little vinegar (yes, vinegar). Wash her hair, then use the mixed conditioner. Then WASH IT ALL OUT FIRST! Then, with a bowl of HOT water next to you, and using the nit comb, start combing, every time you comb, dip the comb in the hot water to get the nits out... comb, dip, comb, dip again and again and again. Starting underneath and working your way up. I did this every day for almost two weeks (my daughter's hair was long!) and it was worth the effort. And, as someone else said, then do it every once in a while just for peace of mind. Also try and find out from whom she's picking them up - that parent may need to be spoken to (hard, but necessary).
Good luck.