Your remark about your cousin touched my heart. :-)
It’s sad but sometimes we don’t help ourselves not even a bit. Lack of self-confidence is a hell. She is not to be blamed sure she is a very nice and a very valid person but the less able we see ourselves to do and get our goals or stand up for ourselves, the easier is to have relations where we can feel or being abused.
As an animal lover the thing about the dog and the cat is pretty normal. They perceive extremely well energy and mood states and when they don’t see you strong enough, their world gets upside down and they have to kind of taking the leads somehow.
She needs to empower herself some way.

Linking the question you addressed to me and the argument you came out with in regards to our own behaviour sort of provoking a mean behaviour from other people...I’m sure sometimes happen this way.
This is my passive behaviour part. I’m very polite and gregarious but when I don’t see the same behaviour in the other person, I mean just want to be treat in the same way, I can move into an aggressive mood and attack as if I had to defend or protect myself and as if I regret being so nice. That’s if you matters to me. If you are not gonna be an important part of my life, I move on and forget about you as soon as possible. I barely will be able to trust in a possible relation with you. It sounds resentment and yes, it is. I’m trying to find a kind of balance and be more realistic with boundaries and expectations.