First of all, most kids don't go from diapers one day to underwear the next. Potty training is a process. The best thing you can do is not pressure her. Talk about it. Read books about it. Ask her if she wants to go. Let her sit on the little potty (fully clothed if that's all she'll do) when you go. Then let her listen and see what you did when you're done. Tell her when she's a big girl she'll do it that way too.
We started this process with my daughter when she was 16 months because I saw her crouching in the corner of the dining room and when I asked her what she was doing she said "poo-poo". I figured if she knows when she's doing it, she can learn to recognize how it feels before it happens. By 26 months (yes, 10 months later) she was making #2 on the potty all the time and by 29 months she was in panties all day. There were times throughout the 8 months that I thought she had it but regressed. That's part of the process. Just be patient, encouraging and don't make a big deal when she has an accident. Clean it up, let her know that she should tell you next time so she can go on the potty, give her a big hug and start over.
We kept my daughter in pullups at night until she was almost three. I really don't understand the resistence to pull ups. I found they worked just as well and were thinner, lighter and more comfortable than diapers. As soon as she was big enough to fit in the smallest size pullup we switched. But anyway, I just refused to convert her crib to a bed. I felt better knowing she was safe in her crib but felt bad putting her in underwear knowing she couldn't get up on her own to get to the potty. As soon as we converted the bed we swtiched to panties at night and over the course of the next 6 months she had maybe four "accidents" - mostly caused by drinking too much before bed. She was ready and had been staying dry most nights for a while.
Take your time. Talk about it and help her understand the process. Let her know it's up to her. She's going to have accidents. Just relax. She'll get it.