Children differ so widely in this area, so I can only offer up what worked for my 2.5 yo (who is now 4). She, like your daughter, knew what to do and was more than capable, but just didn't feel like it some of the time. We tried M&Ms and stickers, and she would only go if she wanted some. That approach totally backfired. So, I went and bought a few new outfits with Disney Princesses on them. (Usually my kids get hand-me downs, and she was totally enamored of the princesses). Anyway, I just showed them to her and told her that these clothes could only be worn with underwear. If they got wet or dirty, she had to wear other clothes. (Unless it was a true accident, and then I would give her a chance with a different outfit). I washed those outfits almost every day for a 4 or 5 days, but she wanted to wear them SO badly, that she was willing to go on the potty to keep them from getting wet. #2 took a little longer, but within a month, she came around.
I hope this helps! Good luck!