I don't think that works very well.
We can only change ourselves, not other people.
Personally, I'd work on myself and accepting my mother the way she is... whether that means having a relationship or not. Remember just because you share someone's DNA doesn't mean you need to like them or have a relationship with them.

I have never really heard of this working, especially since many people start therapy on their own, and the other family member is invited to participate later.

For example, my brother-in-law was in a clinic for six months for alcohol and prescription pill addiction. At the end of four months his therapist invite his mom, and she went with the attitude, "you owe me an apology", which her son was not able to give her, and it ended aggressively.

Same thing happened to my husband, too.

I think one of the inherent problems, is that when you are the child, and invite a parent to go to family therapy, the parent may not be willing to budge from the point of view, that it's the child who "has the problem", and the parent remains in the myoptic stance, "I don't have the problem, because I'm not the one in therapy." That is, it seems that there still exists the point of view that therapy participants are not people attempting to solve their problems, but the people who cause the problems.

I think it can work only if all are very motivated, very insightful into their OWN problems, and are working on those problems independently too.. I am not sure how much this happens..usually it is one person who initiates the therapy whether by accident or design...

Dysfunction does not occur in a void.. especially in families.. and dysfunctional family systems try to maintain the status quo even if it is bad or unhealthy... it take a very strong insightful person to do this.. and it would be hard to find that many families members all there at the same time... staying the same is comfortable even if our actions cause us pain.. the pain we are feeling must be so bad that we are willing to exchange it for the pain or uncertainty before we are willing to try and some people will put up with a lot before they reach this point...

That does not seem like therapy, That sounds Crazy, In my opinion, you really should work on forgiving your Mother and working out your problems because We as parents do not automatically know how to be a parent we learn from day to day and we make so many mistakes along the way, I have made so many mistakes raising all my children and I constantly apologize and sometimes get so hurt by what my Children say but I know that if I just explain things and how they hurt me and how things they do are wrong and how they can get hurt out in the world and how we must respect each other in order to get along then things seem to work out..but I also listen to them and I ask whats hurting them, Remember your Mom also has feelings and she hurts too. Do not say things that will hurt you in your future. Sometimes we become our Moms and we end up hurting our Children..
Take care, Cathy