I said horrible things because I was pissed

I spoke ill of my mother last night with a sibling of mine she was being rude to me yesterday and I took it personal I just felt attack then I just said some things I didn't mean she found out that I was saying those things she will never forgive me I guess she has disowned me I feel really bad I didn't mean to say that about her I was just really mad. Any advice on what I can do?