I assume that's the problem because it makes sense, but I don't think that when I have the problem, I just get a strange desire to be abusive towards the dog and clench my teeth on something at the same time as hard as possible.

I understand small dogs are annoying, but I also know for a fact that this is different than annoyance. The dog is very well behaved, it's seeing her curled up sleeping on a bed or wearing a shirt or seeing her trot that gets my anger going, I feel it deep in my stomach. Basically seeing the dog being unassuming and carefree pisses me off

In fact, just now that I've started typing this, it occurred to me, I have a desire to abuse the dog while pretending to be nice to it. Dropping it in a pool of water or petting it while it's quivering in fear. I assume this is because my sister was passive aggressive and would be as vicious as possible while still maintaining her facade of being the good one. I don't know, it just popped in my head.