How about tangible reinforcers? Perhaps, she's always getting what she wants so if she doesn't have access to one thing, she still has plenty of other things.
Finding salient reinforcers is the key to modify a behaviors.

There is just nothing that seems to be important enough to her that if she doesn't get to do it, she cares that much about it. She will fight to not go potty, but then she'll be on there and will be doing whatever it is she's doing and won't want to come off.

Hugs to you, OP. You're not alone.
Does your DD have issues with low muscle tone and also not being flexible (doesn't want to stop in the middle of an activity to go potty)?
What's really motivating her? Maybe use the strongest reinforcer for toilet training and she can get access to that reinforcer only when she goes potty.
My DC loves to watch youtube video clips. Every time DC goes potty independently, DC can watch one video clip. DC gets bonus video clips for staying dry all day. Other than that, DC has no access to iPad.

OP here, we were going to go to Georgetown Pediatrics for Gastro, but were cleared as not constipated anymore. Children's seems to be the only people covered by our insurance, so I think we may be stuck. I'm seriously at a loss right now though. We have done everything. I have been doing bladder retraining for over 2 months (have her go every 2 hours, sometimes up to 3, but mostly 2), she drinks a specific amount of liquid every day, which I have to monitor how much and when to know if she will need to go to the bathroom sooner, extensive incentive programs that even psychologists and behaviorists have said they can add nothing to. Despite all of this, we are still having accidents. Today she completely wet herself and didn't even say anything, just kept playing. I have no idea what to do at this point since no matter what I try, it fails. I feel bad, but I inevitably get frustrated with her and it shows. We try to talk to her about it, but she says she doesn't want to and gets upset. Hell, even getting her to go to the bathroom can be a battle many days, which is why there is no way I can get her to go more often than I do (6 times over 12 hours), without her resenting it even more. All the literature out there seems to be on nighttime wetting with daytime wetting. Kids who just wet in the day are very rare, so no idea what is going on.

Avoid Children's National Medical Center. In our experience, they have very little time or attention span for issues that are not extremely complex (not discounting your child's issue - just noting that they will likely not treat with the same attention as they would were it a very complex one). We have had luck with Georgetown Pediatrics. Have also heard that Johns Hopkins has a good center.

OP, I could have written your post. My DD has the same issues!
Which doctor are you currently seeing right now (that evaluated the x-ray results)?
We saw Dr. Kerzner, who recommended Dr. Kalloo. I thought Dr. Kalloo's recommendations were "generic".
We are going to give her another chance and see her again later this month. But we also have an appointment with Dr. Rekhtman (gastroenterologist).

OP here. Thanks for the information. I actually have the "It's No Accident" book, and we were going to proceed along the lines of Dr. Hodges, but our doctor has done x-rays and even a digital rectal exam and says that she is clear, so it may be a urological issue since she is not responding as well as we would like to the behavioral strategies. She is on a timed voiding schedule and has an extensive incentive program, but accidents are not predictable. They said we needed to get some tests done by a urologist, but now I'm not sure who to go to if the people at Children's are no good. I know there is a Dr. Gibbons and a Dr. Pohl around here, but they may only be interested in more interesting and complicated cases, and I want someone to take my child seriously and do all the necessary tests. Any ideas?

I really did not like Children's or Dr. Kalloo. The downtown clinic is a mess with appointment times, the staff was rude, they gave out incorrect information about scheduling tests, and they basically just give everyone the same one-size-all schtick (and are pretty condescending about it).
The staff and NP at the Fairfax office are better.
Search this forum as there are a TON of postings on the wetting issues. Read It's No Accident -- it will be more helpful than the doctor's at Children's (although the doctors or NP can rule out certain physiological things). If she was constipated, she's probably lost muscle tone and its going to take her a while to build it back up to restore her urinary control.

My daughter has been struggling with daytime wetting since she was potty training at 2.5. She is now 4.5 and still having difficulty. She also has constipation, but is being treated for that and have been told by the gastro that she is clear based on x ray and physical exam. They say its time to pursue the urology route as behavior therapies have made minimal improvements. I'm looking for a pediatric urologist that will take this seriously since I know they like more exciting issues. I know Children's has a voiding clinic, but don't know much about it. Is anyone familiar with them and Dr. Kalloo or anything similar?