I've never heard of a female cat spraying. Strange. But my theory about this is that they do it to mark their territory, especially strays, because they are making their hunting grounds and warning off intruders. If you have other cats in the house, the same thing happens. Cats will stake out territory even inside the house. My guess is that she might stop if she's in a home by herself without other cats. She may mark her territory at first, but then she should stop.