[Megs]

The vet looked at her urine and said it was fine. I am guessing they just did a dipstick and spectrometer, though, as there certainly wasn't time for a culture.
The vet also felt it was unlikely since she has been on antibiotics every couple of weeks, it seems. (3 surgeries and 2 infections in the last 3 months)

think it would be wise to request a culture? My vet has NEVER offered this, but I know they do it at the human doctor.

Heavy antibiotics may disrupt the balance in your girl's natural flora, which could increase her chance of developing a UTI. If the vet has not actually ruled out a UTI, I think you should have them do that.

Hope your girl feels better soon. Three surgeries and 2 infections in the last 3 months? Since she's not even 6 months old yet, I'd wait to spay her based on that alone; unless it's a medical necessity or something. That seems like a lot of anaesthesia (and antibiotics) for such a young girl.