Hopefully, you are SI ing because you didn't learn how to deal with your emotions in a healthy way and this learning didn't happen because of your parents. Parents don't teach because of their problems. You write that your mother "flys off the handle" when you tell her things and I'll bet that this always happened and it affected you greatly. Our parents usually don't change (unless they are working on it in therapy) so for you to wish and try to change her would be very frustrating.

When I first heard of SI as a social work student I was perplexed and the explanations that were available 15 years ago were not adequate at all. I have been able to understand it over the last 5 years by asking people why they do it and finally gaining info from others in the mental health field who have expertise. So the understanding of it does not come naturally.