I presume you've done all the "optimising bladder health" stuff, in case they're trapped in a cycle of really nasty bladder irritation?
Roughly speaking....
Drink loads of fluids. I mean loads. At 9 yrs old, that'd be about a litre and a half of fluid (and a bit more from what they eat). The fluids need to be really spread through the day - so much easier when they're on holiday, and not trapped at school...so many seem to drink most of their fluids around teatime! Water/squash fine, milk okay, all fizzy drinks, caffeinated drinks, and fresh citrus drinks totally banned.
Watch for any signs at all of constipation, and treat thoroughly (constipation both makes the bladder not empty well, so stale urine is left behind, which is an irritant, and leaves more bugs floating around down below).
Make sure she doesn't hover, but sits on the toilet, and is certain she's finished - hovering and dashing off also lead to poor emptying. I'm sure you've stressed all the proper wiping stuff already.
You've probably already banned all bubble bath. As much as possible, just use water in the bath/shower. Where you really need to use something, use a product aimed at children with eczema, like oilatum bath: when they're caught in a vicious cycle, then the urethra gets very sensitive, and reacts to almost anything, and that both gives you cystitis symptoms, and makes it easier for bugs to get in. Don't know if you wash her hair in the bath, but if so make sure she gets out straight after: even the mildest shampoos are very irritating down below.
Hot weather can make things worse, so aim for ventilation: cotton knickers, avoid tights and leggings.
Look at her pattern of weeing when she's well. To get her bladder healthy, you want to see watery dilute urine (dilute lemonade appearance, or watery). If it's strong or yellow when she's well, it helps show she does need to drink more. Make sure she's not "hanging on" (some kids, for instance, hate school toilets), as hanging on can lead to a few drops leaking, which can again irritate things down below.
Oh, and slightly odd one - if she's been on loads of courses of antibiotics, might be worth trying probiotic yoghurts, as she might be getting an imbalance of bugs in her gut, which spread onto the perineum, and can then can cause local problems. Is she ever sore down there?
Anyway, if you've already tried all that lot, which you may well have done, then you need to ask her paediatrician (please tell me you haven't just seeen the GP!). But if not, then try giving it a whirl. Works for quite a lot of kids, and when it doesn't, then you know it's really worth pushing for more answers.
Hope that helps.