If this is a NEW behavior then she really needs to be seen by her Doctor as something medically could be going on..

If this is just how she has always been , well chances are your not going to really expect her to change at this point are you ? No I think not.

I am a bit confused about there being some trauma in the past and a Therapist telling you to just "avoid her" .. If your being triggered you need to get into therapy and find out the cause of it and how to recover adn come to terms with it. . You will also learn coping skills and ways to interact with your Mother that is healthier for you and her.

There's no quick fixes in life sadly enough.

I wish you luck in whatever you decide.