Sometimes, sadly, there is nothing you can do. Just treat her kindly and respectfully (even if it's hard, because I know it can be!) and keep in mind you have every right to be involved with him, as I assume you're both over 18.

And if nothing else, being consistently nice to her will probably drive her crazy. Even if I don't follow the Christian path, I do love the verse saying to "be kind to your enemies, and bless those who curse you, for it will be like heaping burning coals upon their head".

I'm 20 and he's 19, gonna be 20 in a few months, so yeah. :/ But she can interfere by stealing his car, house keys, cellphone, etc since he lives with her. Maybe we can get a place or something.

That's what I'd recommend. It seems to be a highly toxic atmosphere no matter who is involved.

I'd recommend him (and by proxy, you) getting as far away from that as possible, ASAP.

I'm honestly at a loss with this. I guess the best you can do is find out why she dislikes you so much, and then try to not do the things she dislikes around her? x.x