Her bladder may not be large enough to hold her through the night--especially if she is sleeping 8 or more hours straight. If she's light enough to carry to the potty, sit her on it a few hours after she falls asleep (I often put my 2 year old on the potty just before I go to bed (around 11 pm) and she'll pee on the potty and never wake up ;)
Sometimes it's all a matter of what is eaten/drunk before bed:
Do a trial period where you don't give her any liquids except water after noon. See if that helps.
And there are some people that have trouble because of food sensitivities:
Dairy sensitivity and gluten intolerance (as well as celiac) have also been linked to enuresis. (Other food sensitivities can also cause bedwetting, but are not as prevalent. Personally, I don't bedwet, but have to get up 3 or 4 times a night if I am consuming significant amounts of soy--Didn't affect MY potty training, because we didn't have any soy in our house when I was a toddler :D)
If all else fails get her some cute cloth diapers instead of pull-ups. Have her pick out the designs (check out some of the WHAMs that sell cloth diapers there are a lot of really cute designs and prints) and explain to her that they are her night time undies. Don't call them diapers and don't think of them as diapers, they are NITE-TIME undies to protect the bed if there is an accident, you should still try to be proactive about taking a night time potty break anyway.