In Reply to: Why is my cat doing this? I have a female cat posted by sm on April 26, 2007 at 19:01:40:
where a small part of hormone producing tissue being left behind and it regrowing years later and producing hormones. It could also be just boredom/spring fever. It could also be a learned behavior (especially if she was spayed as an adult cat).
Maybe try getting a figure 8 halter and leash and take her for walks. That way you can control where she goes so she doesn't get hurt or lost, but still allow her to visit the great outdoors that she is missing.