Great suggestions here. I'd try her inside in case it's stress related, but any females I've ever had with a 'peeing outside the box' problem have had urinary tract issues. If you can catch early on, it's may be reasonably easy to control with diet, lots of fresh water/wet food, and scrupulous litter box cleaning. Good luck and I'm so grateful and uplifted to be reminded that there are so many caring people like you!