hi there!
some of the parameters on the tests strips are not accurate for cats and dogs. Can you tell us what urine infections she gets? Has a sample of urine been tested and cultured by a vet? What was the bacteria that was detected? Ecoli is a common one and is a result of the urine being too dilute, urine becomes too dilute for a number of reasons, mainly poor or aging kidney function. Were there stones or crystals detected in the sample the vet sent off? (If it was sent off).
A lab is the only way to be sure of an infection, that is where the Specific Gravity is tested, alone with microscopic examination for crystals, blood (haematuria) and bacteria. When the urine is cultured in a lab, the bacteria present are grown to see what species they are, then a sensitivity is done, this determines which type of antibiotic should be used. Test strips alone are not much help and are mostly used for glucose testing, however they are useful for certain indicators e.g microscopic blood, but even then to be sure of infection it needs to be sent to a lab.
If her infections are ecoli, then there is a very safe supplement you can use called D-Mannose, this keeps the bladder clean of bacteria and can be used as a maintenance dose with or without antibiotics, but doesn't actually kill bacteria (and only works on ecoli) Either way, re-occurring urine infections absolutely must be treated with a long course (6 weeks) of the right antibiotics, because ecoli burrows into the walls of the bladder often avoiding antibiotic therapy only to emerge and infect again. Urine infections are no at all common in young cats and dogs, is your girl getting on?