Are Siamese cats more prone to being sterile?

I adopted a Snowshoe Siamese about 6 months ago. She was a year old at the time. She is nice to humans and fine with my other cats but kinda anti-social. She won't cuddle with the other two but she will play with them on occasion. I recently took in two momma cats with kittens and she is not happy. She has started to urinate everywhere. I have tried everything She recently went into heat and I was told she was spayed. The vet confirmed she was not spayed. She lived the first year of her life as an outside/inside cat and has escaped twice while with me, once was when she was in heat and my son left the door open a second to long. Could having her spayed help with the urinating thing? The vet said she may be sterile seeing that she has been outside and never gotten pregnant. Is this common?

Sterility is unusual but if she had subsequent heats without being bred that can lead to sterility from ovarian cysts (hence why breeders don't like to wait more than 3 heats before breeding). And yes I do think spaying will help many of the behavior problems. While she is away for the spay, do a thorough cleaning to make sure the urine smell is out of the carpet using a special feline product that breaks enzymes. We have a lot of issues in this regard with our whole cat and its quite common for whole cats to pee and spray everywhere.

If she has cysts formed then it is in her best interest to spay her as this could be cancerous later.

I made her an appointment to be spayed on Tuesday. I really hope this helps as she is ruining the carpet and I live in a rental

It might not be immediate as the hormones will need to wear off but it could also be an immediate improvement, and either way it wouldn't be long to clear up. Time will tell. Everything you describe sounds very much like a whole cat and not unusual in the least.

The antisocial thing though could be a couple things. It could be the cats not really liking her because she smells funny (we go through this with Meeka being whole and the others aren't, they often don't like her smell and don't know whats wrong with her when she is in heat). It could also be completely unrelated as she might just be a bit of a loner anyway.

Peeing/spraying behavior is soo common in whole cats. I know someone with a whole siamese who refuses to get her spayed. At the same time if she dosen't stop spraying in his room he wants to give her to the shelter. A lot of people don't realize its a natural response. This is how they attract males, through spreading their scent.

My girl likes to pee in all teh corners of teh house and at each door. I keep mats down in her favorite areas. Still a lot of work.