Lauren,
Hello. I agree with the other posts that you can't train at night. It's when their body is ready or not. We used pull-ups at night (called them night time diapers, but they had that pull up factor like underwear) until she was dry for 3 weeks every morning. Then we moved to underwear at night too. I would start getting into the habit of using the potty right before bed now and that helps when her body is ready to not go all night. My daughter use to be soaked in her night time pull up for a long time, but then all of a sudden she started becoming dry (acutally closer to age 3 for us). Your daughter will get there too, it just might take a little longer than you'd like. Best of luck.
~ J.