Oh, having read your extra updates I agree it is probably not medical. When you said you were cleaning up all the time I assumed it was a constant problem every day and everywhere rather than a few times a week from time to time, and never at school. It really doesnt sound that bad now - I would think she will probably grow out of it fairly soon. Even if she is just being lazy, she will reach a stage where she doesnt want to be in wet pants.
I know it is a nuisance but she is still young and the fact she is wet at night suggests she is slower to mature with this aspect of her development - hopefully though she will get there in her own time.
Reading through the list of things you have tried, the only one I would persist with is telling her calmly to change herself and take her wet things to the laundry and wash her hands. Other than that I would concentrate on some mild praise if you see her come in and use the toilet when she is out playing and if you see her "doing the dance", go to her, stop what she is doing and say something like "time for the toilet now, I will let you go by yourself and if you do a wee, you can [have a snack/some extra playtime/some small reward]." If she refuses, say "okay, but I dont expect to see wet pants so dont forget". If she does wet them just say "that's a shame, next time I remind you, please come in to the toilet. Now go and get changed etc"
Stay calm about it and see how it goes.
Maybe you should keep some sort of diary/list over the spring/summer of how often this happens and where she is/what she is doing/time of day etc. Anything that you think might be relevant eg what she had to drink recently. That way if she doesnt stop in the next few months, you can get more advice with some concrete information to back you up.
My only other suggestion would be to try the forum on the ERIC website.