I have a pug who is like that. She is spayed. But she just don't like anyone. So she has to be watched, and there have been some good fights between her and my 14 pound (nuetured) male Yorkie, that I have had to jump in on and litteraly peel them apart... BUT I would never re-home my pug. She is never left alone with any of the other dogs and is NEVER allowed around the small yorkies.
We just deal with it and know how to handle her. Don't get me wrong...everynight she is on the couch with us, with my Chi and my 14lb yorkie, she just has to be watched. usually its a trigger over a treat, food, or a toy. Oh and her bed. NO ONE can go near her bed.
She was my 1st and was spoiled and then we slowly added. She's 8 years old and she's not treated like the little baby anymore, so I can understand why she's so bitter.
But I don't love her any less
She's actually a very good dog. I love her very much!