Am I wrong to give the cat back?

My friend was leaving town for a couple months and didn't want her parents to take care of her cat. I offered to take him but I live 3 hrs away from her parents. We agreed that if things didn't work out, I would meet her parents and give the cat back to them until she got back home.
Well...everything was great at first until about a month later when i realized he had been peeing (not spraying...peeing.) in a corner of my townhouse that I hardly ever go near. If anyone knows cat pee, they know what a strong odor it has. Obviously I had to replace the carpet in that area. I sprayed petBgone on this corner...so then he pees in a different corner. I can't have a cat peeing all over my house. I have been keeping him in our large bathroom with his litter box until arrangements can be made for her parents to meet me half way to pick him up.
My friend is sooo mad at me for wanting to give him back. She says I am not giving her cat enough time to correct his habit and that I "obviously don't love the as much as I love my dog (who doesnt pee on the carpets!)"
I think that I am doing nothing wrong by wanting my house to smell nice and be sanitary.
She is sooo mad at me and says I am not giving him a chance.