I'm afraid I'm not going to be the advice you want to read. We had a really hard time with our last child, who wasn't potty trained by 3. She never seemed to get it, and we had trouble in kindergarten, too. FINALLY, during K, we took her to see a pediatric urologist and discovered that she had chronic bladder infections. The problem ended up being that she would empty her bladder, she thought, but it would only empty half-way, and then she'd end up wetting her pants. We went through a variety of fairly non-invasive tests, and only one that was kind of yucky -- they did an ultrasound of her bladder in action, which meant they put a catheter in, and used it to fill her bladder, until she peed on the table where she was lying. She didn't like that, and it must have felt really gross, but we were be able to be at her side the whole time, and it didn't really hurt all that much. It was just really embarrassing. But it did prove that she wasn't having problems with urine also refluxing back into the kidneys which could cause permantent damage in the event of a kidney infection. And that was good. (This wasn't done until she had a bladder infection and such a high fever that she was dumping sugar in her urine, too.) typically, we were told, bladder infections don't cause fevers, which is why the office was concerned about a kidney infection.
Our youngest was on macrodantin for a while, which is a very low grade (inexpensive) antibiotic that focusses on the bladder, to prevent infections. She was able to be dry when she was infection free.
So that's the horror story part. We were initially thinking that the problem was volitional and she just didn't want to bother to go to the bathroom. In the end, the doctor did tell us that it wasn't. Her bladder was just going to take more time to finish maturing. She's 13 now. And dry. . . but every once in a while she doesn't "quite" make it, and at those times, she starts voluntarily drinking cranberry juice which helps to cleanse the bladder, and she is fine again.
If there are any issues with bladder infections, or if there aren't, but she's got a not-so-grown-up-girl bladder, I would recommend introducing something like cran-grape juice, or cran-strawberry -- something that will help to keepher bladder infection free. And use pull-ups so she isn't embarrassed by her problem. You can sit and read together while she's on the potty, and try to enforce it, as a regular thing activity-wise, but try not to discourge her, and be sure she's getting something with even a little cranberry juice in it, because if there's an infection lurking, the cranberry juice solution avoids antibiotics and helps her body learn to fight the infection all by itself. :-) (the infections came because the bladder never fully emptied, and the cellular waste that sat in her bladder got stronger because she wasn't drinking much because she didn't want to wet her pants, so she was dehydrating and the urine was getting stronger and stronger until she got the infection.)
hopefully, you aren't facing the 5-6 years of regular doctor visits we went through until our daughter was able to hold it and use the toilet without medication, but know that it's not uncommon and there are some excellent pediatric urologists out there and visits are "easy" -- no shots. Ultrasounds of the bladder, but other than that it's mostly talking. :-) I wish we'd started our daughter sooner, because it would have saved her a whole lot of embarrassment.
good luck !
barb
She ended