Maybe she is angry that you have the courage to do what she doesn't.
My mother also gets angry with me about stuff like that. She is an ACOA, and untreated at that. I was in an intervention course a while back and they wanted me to go to meetings to write a paper on them, and she actually refused to watch my son for me while I did it. Literally. Because of her extreme denial about the situation, she was willing to let me fail a class.
Let me tell you, it's just as bad being the child of an ACOA as it is being an ACOA.
She is better now, especially because I am dealing with my own stuff with my ABF, but I still remember how she made me feel because of that. So I know what you are talking about.