L.W.
If you want to rule out an infection, you can make an appointment with her doctor of course. But first, have her drink lots of water and cranberry juice. I personally take cranberry pills because I don't like the juice. Every time she eats, goes to the bathroom, walks by you- whatever works. If it's an infection that will get rid of it quick, I do that whenever I feel symptoms coming on, and they always go away in 1 or 2 days. I've only had to be treated once by a doc when I was a child. If it's not an infection then it could be that she is holding it too long before she goes. Figuring out why and how to stop it may just take lots of patience and persistence on your end. Make her go to the bathroom more frequently, and talk to her about if something is bothering her, or why it's bad to hold it etc.