need help w/PTing

DD has been showing signs of readiness for PTing since she was 18 months. We've tried everything to get her to go, but she just won't do it. She sits on the potty and nothing happens. We tried enticing her with candy, stickers and big girl panties.. She watches me go all the time. We tried putting her on the potty every 30 minutes. She tells us when her diaper needs changing. 

I realize they don't do it until they're ready, but I would really like to help her along b/c she's getting bad diaper rashes that she never had before. I assume it's b/c her poop and pee are changing as she gets older.

I appreciate any tips you can share. Thanks!