Urinating on the dirty clothes

When I got home from work yesterday I started a load of white clothes. I noticed that Dori had urinated on one of my bf's socks. I was suprised because she hasn't ever gone anywhere other than her litter box with the exeption of once before she got spayed. My bf had accidently let the neighbors outside cat, Socks, in with him and he was in for a few minutes and I thought that maybe she urinated on them marking her territory, or even that possibly Socks had done it.
Today I went home at lunch time to check on her and she was sleeping in the dirty clothes pile and there was another sock right next to her that she had peed on. I was confused because I thought that cats wouldn't sleep where they used the bathroom....
She has a vet appointment on Monday and I plan to discuss it with him. I know cats will urinate in various places when they have a UTI, but I am wondering if this sounds more like she was marking her territory since Socks was there She doesn't seem to be acting sick at all. She was playful and is eating and drinking and using the litter box with the exception of these 2 times she chose to use the socks.
To be honest with the breathing problems she has been having I have a bad feeling that something is going to be really wrong with her when she goes to the vet

I would get to the vet as soon as you can. My baby, Eddie NEVER went outside the litter box in the 3+ years I owned him. When he finally did, I thought oh well and waited a few days. By the time I got him to the vet, he had crystals and was not able to urinate at all. Until the morning I took him to the vet, he acted normal in every other way, except for some excessive licking. But my cat is a bit obsesive any way. I would get to the vet and rule out any type of medical problem.

Your apt. is coming up tomorrow or Friday right? I'd keep her out of this area, and see if she does this anywhere else...it could be a sign of a uti, or she's marking for the reasons you noted.

I know you are worrying, hang in there, you will get your answers, and take it from there...one step at a time.

It definitely could be a urinary infection of some sort. Willow was occasionally peeing in other places but using the litterbox the rest of the time. It turned out she had a lot of bacteria in her urine. She's on her second round of antibiotics.

There is another possibility. Were your boyfriend's socks washed in bleach? Sometimes cats are attracted to bleached clothes and they like to pee on them.

Let us know how she is after her appointment.