My advice would be not to push it and let it happen when she's ready. It seems to go best, when it finally just "clicks" and they "get it." My daughter turned 3 on May 3, and even though she has been going in the potty since before she was 2, she didn't mind sitting in her own mess. She could go in the potty every time you asked her to, but she didn't think of it on her own and would still go in her diaper. We got to the point, where she would only get a treat (skittle, small candy, sticker) if she kept her diaper dry in between going on the potty...it didn't work. She finally was trying to go on the potty and had waited too long, so she peed all over the floor in the bathroom and I think she was so embarrassed, it just clicked. She's been going on the potty ever since and somehow stays dry at naptime and all night long (she has a small potty in her room and can go on it when ever she feels the need to). I have friends who have turned it into a struggle and it is not fun--b/c it's one of the things that they can control and they know it (same with eating/food issues). I also have another friend whose daughter potty trained herself a month before she turned 3, then 4 months later kept having accidents. The doctor said that this can happen within the first year, after they are potty trained, b/c they wait too long (b/c they're too busy playing) and then they have accidents. So just know your child will do it when she is ready and just try to be patient. Not sure about the holding it for so long, until she hurts part. Will she go poo in the potty? That might have something to do with it? There are lots of videos at the library to check out...Elmo has one, Bear in the Big Blue House, the one with the red cover (I think the girl's name is Prudence!)...you can also try letting her roam the house with nothing on, or be outside in your backyard. When my daughter was still learning, she had a hard time distinguishing panties from a pull up or diaper, b/c something was there. Another idea is to put panties on and then a pull up or diaper--then they feel the wetness, but it doesn't go everywhere if they do go in their pants. Know we've all been there and had our own struggles with this, but they all get it eventually!
GOOD LUCK!
A.