I'm sorry your girl isn't feeling well. You will want the urine culture. This may require a clean draw sterile sample direct from the bladder. The culture basically determines which antibiotic kills the bacteria, therefore, getting the appropriate medication. My dog was much older, but we had one UTI that took 3 months of antibiotics to clear (note, my dog was a senior and had a compromised immune system at the time).
One thing to check is your grass. My dog was a short-legged breed and the vet felt that she could be picking up bacteria from tall, damp grass. Keeping the grass mowed short did seem to decrease the frequency of her infections until the immune system issues. You might want to try keeping your dog out of the tall grasses if she has access to them.
You ask about her time in her kennel. At 7 months I would think 4-6 hours would be OK, especially on the lower end. But until the infection gets cleared up, she may have issues. I've heard that pups typically can hold their urine the number of hours equal to their age in months. But typical doesn't cover every dog. With the infection you do need to make sure she has ample opportunities to empty her bladder so she can rid herself of the bacteria. Your vet could tell you if her kennel time is too much, based on her current health.
I know it is frustrating. Good luck.