The phrasing of the second part of her reply sounds a bit clumsy to me : 'I'm glad you were able to be there for your sister'. I don't know why she is glad, it's your life, and I don't think she should be glad either way. I guess perhaps you would have found it more helpful if she had responded more to your feelings about your sister's state and about her snapping at you, which sounds sounds upsetting?