I don't know how to feel about this (may be long)

Okay so recently I cut again and I was over two months free of cutting, and my mom caught me doing it. She was of course upset. And I told my boyfriend that I did and he was mad for two days but we talked about it today and we're good now. But yesterday, my mom got me a cat as an early Christmas present and coping skill. I love Lizzie to death (I named her that after my friend who died of bone cancer a few years back). And she is very friendly and cuddly with me, and only me. But when my mom or anyone else comes into my room, Lizzie growls. I don't know if it's because she's frightened of them or protecting me. I don't know, what do you think?