Hey V.,
My daughter is almost 3 years old. Her older brother is almost 4. (1 yr & 3 weeks apart) Anyway, she's known what to do and has for a while now, but just didn't WANT to. Until this past week though, she went potty for her prek teacher at school! So this past weekend, she's been in her underwear & pullups. I think that if u are going to try to train her, u definitely have to cut out the diapers. Even though its okay for her to go in a pullup, it's a "big girl" thing. Besides the fact that pullups are easier for her, and you, to pull down and pull back up. I have this book that I used with my son and showed u how to tell them to pull their pants up and down. Hand in the front, hand in the back, and it's worked really well for both kids.
Anyway, if she wants to sit on the potty, I would let her. She'll figure it out. My Emma has had some pee accidents, but like I said, the pullups will help with that. She also likes to just sit there.. and she has also no problem in doing number two. Which is great!! Because I had the reverse problem with my son. He would pee okay, but not poopie. That was always an accident at first. So i'm thinking that this is still good..., I hope! She'll get the hang of going number one and getting to the potty in time, etc.. just happens in their time. But I would also try to make it fun as well. With Emma, we are doing stamps. Simple little stamps that wash off in the tub. But she LOVES it. Find something that your daughter loves and use that as encouragement. Like if you use the potty, you'll get a sticker or something. But I think deinitely rewarding her with something. Make it fun and get the pullups.
Anyway, hope this helps.
K.