I think that's a great idea....talk and/or write out a note to mom with your thoughts and feelings.
I don't think it's at all fair to assume that just because someone has been angry and is letting it out, that they have a mood or personality disorder. Is it possible that adult stressors turn into frustrations and the place they feel most comfortable letting it out is at home? Of course it is. Does it make it right that they put it on their kids? No...it doesn't....but it also doesn't mean that they are doing it intentionally or that they are ill either. And sometimes, in the heat of it all, they don't realize how hurtful they are being.
Finding some quiet time when everyone is in a good mood, one can start up a conversation and say "Wow, mom, it was pretty obvious that you were stressed out yesterday. Is there anything I can do to help you with your stress? Can I tell you how it makes me feel when you lash out like you did yesterday? I love you mom and it hurts me to see you having such difficulties."
Now, I'm not saying that kids need to be their parents therapists. What I am saying is that sometimes, kids can be the catalyst to more open and honest communication. Regardless what age we are...reaching out to someone we care about is what love is all about no?
(((((((((((((( selfy )))))))))))))))) I know it's hard to be the brunt of such anger and stress. I'm sorry you had to experience it. I can tell that you are worried about your mum. I hope she feels better soon and the two of you can do some heart to heart talking.

sabby