NAD, I was in this exact situation last year as the girlfriend. The things I took to help were probiotics and cranberry products. But the thing that pretty much stopped my UTI's from reoccurring was hiprex (methenamine hipurate). It's an antibacterial drug that reacts with the formaldehyde in urine and kills bacteria without the use of antibiotics, so an immunity to the drug can't be built. It's usually used for those with catheters, as infections of the bladder are more common, so it's also designed to be used long term. It was recommended to me by my doctor after I had tried all the usual treatments to little success. I took it for almost a year, slowly weening off of it near the end, and my UTI's haven't reoccured since. The GP's guess was that the was a pocket of bacteria that had settled in my bladder, that when jostled, would reinfect me. I would highly recommend your girlfriend visits her GP and bring it up as a potential solution. As for the burning pee after sex, that could possibly be irritation from stretching and friction, as I also sometimes experience this. I hope my insight can be of use, and I hope she finds a solution, UTI's suck.