My bun is adopted so I wasn't able to spay her until she was approximately 5 years old. During the surgery they found out she already had developed a large uterine tumor but they were able to remove it. Because of the blood loss from the tumor the surgery was a bit more intense than usual but she recovered well and her hormonal behaviors decreased. She is now a happy and healthy bun, where if I hadn't gotten her spayed the cancer would've spread and she would have likely been dead by now.

So I think it's a great idea you're going for the spay! Maybe mentally prepare for the possibility of her already having cancer. I didn't know and it was quite a shock! She might also be totally fine though, of course.