Is the cat fixed? If not, that could be the problem. At 11 months, that's about when they start that stuff because they are maturing sexually. If you get her fixed, she'll likely stop eventually. At least she's not a male!! It smells really, really bad!! I fixed my cat at 7 mos and he's never given me any problems in 5 1/2 years. So unless the cat is sick, she probably needs some fixin.