E.B.
I agree with Rachel's response! I was a nanny for several potty-training-aged children and it worked the best! You just have to let her have a few accidents, she will HATE the feeling (wouldn't you?) and she will very quickly realize that the only alternative to that yucky feeling is to do it in the toilet. Just stop giving her diapers one day. you can say "oh, I’m sorry, we ran out of diapers and I can't go buy more right now" and she will either have an accident or go to the potty. I would suggest putting her in some clothes that you REALLY don’t care about and can just throw away for a few days---- you can buy cheap little leggings or pants at Walmart for about $5 each and some inexpensive underwear that you can just throw away. So even if it happens for 3 days, you are spending less than $20 for a potty trained kido— totally worth it!
I think the big thing though is not to punish her for accidents. Don’t praise her, but don’t punish her. Just say "ok, I’m going to clean you up now, if you go in the potty this won't happen." but don’t punish her. That way when she quickly decides that the potty is better than poopie pants, it will be her decision, not something that she is doing to avoid getting in trouble. She is much more likely to stick with using the potty.