Spaying will make it worse. You may want to consider keeping them separate in the house on a permanent basis. Each gets their own time. I've managed multiple gals, and gals are territorial. Some do get along fine, but when they don't it will have the outcome of a to the death fight. If you aren't already using crates, you should start now, always when unsupervised, to be sure both gals are safe. It is best if they can't see each other. With my two, I had one in the hallway and one in my living room. Each got time outside, walks, playtime, but never together and they got along better simply because they didn't have to deal with each other. They also had the defined territory of their crate, and I never allowed the loose dog access to the area where the crated dog could see. Baby gates work well for their. It’s a bit of work, but if you love both dogs equally, as I did with mine, rehoming is not an option and you just have to understand that both your dogs are incompatible personalities, even though they both love you. You can try a reintroduction on neutral turf, like a park, after a month and if they are OK, try integrating them back to main areas together under strict supervision, and see how it goes. If not, at least you know you can manage living with both of them separately. I wish you the best of luck, it can be difficult to have two dogs that just don't see eye to eye in the same house.