Getting Prissy Spayed

I have had my prissy dog for several years now, and in all this time, I have not thought about getting her spayed, except for the times that she comes into heat and our male dog, Shorty, is bothering her. She does not like Shorty and sometimes she can be very cruel towards him. Of course, what female wants to be bothered when they are having their time, right? Anyways, Prissy is showing me a side of her that I don't even like very well, and that's the fact that she has been tinkling on my sofa, the floor, the arms of the sofa, soft blankets and whatever else she wants to "mark" and I believe it's because she is in heat, or maybe coming into heat. I have not bred her, I think that she's way too tiny, and Shorty is not from the same litter, but they do have the same parents so that was never an option. I have made the decision to get her spayed and I have been reading that it's a good thing, that it helps them live longer lives and I am hoping and praying that it will stop her behavior of having to mark things in my home.......otherwise I will have to buy some diapers for her, and I really don't want to have to deal with that expense.