Welcome to MS.
I am glad you have found this place of healing and support.
It is understandable that the thought of seeing those who harmed you would bring forth a lot of anxiety and rage.
Cry and find other ways to express those feelings so you won't feel like you are going to explode. If smashing things makes you feel better, perhaps you can smash some cinder blocks with a sledge hammer (wear eye protection). There are a lot of ways in which you can release these feelings without hurting yourself or breaking things that you didn't really mean to break.
Before you go to your mother's, you may want to create a few exit strategies for yourself. Plan ways in which you can leave the premises or the activity. Practice what you will say if you are questioned about why you are isolating/ leaving. Knowing that you have an "out" may make it a little more tolerable to be there.
It is also important that you tell yourself, and believe, that it is "ok" for you to leave. If all you can manage to do is walk in the door, wish your mother a happy birthday and leave, then that is what you can do. Do not force yourself to stay to the point where you are so uncomfortable or enraged that you lose it.
Taking care of yourself is not only important, it is a necessity.
Having an exit strategy is part of your self care.
Though you do not yet know us, know that we will be with you while you are at your mother's. You are not alone.
Take your time and look around. You do not want to trigger yourself by reading too many posts at one time.
At your own pace, read the boards and wander into chat. The lounge (chat) is open 24 hours a day though it isn't always populated.
We also have moderated chats called Healing Circles.
They meet on Sunday and Wednesday evenings at 9pm eastern time and one on Tuesday at 19:00 UTC (European and African time zone) which translates to 2 PM Eastern US time zone. The Healing Circle on Tuesdays is scheduled to resume in September.
Again, welcome to MS.