You know, many a meeting both in AA and Al-Anon has been started on a 'resentment' and a coffee pot. New meetings all over the world have been started for many reasons, but 'resentment' is one of the reasons.
So ....................................
Talk with some of the other members and see how they feel about this, offer to have a meeting, since you say it is a small group, in your home once a week.
Nothing wrong with starting a new meeting, having a 'group conscious' to set the 'meeting guidelines' and go from there. If it becomes a regular meeting, you'll know in about 6 months, then you can find a place, other than your home to hold it.
What you have described is so far off of an Al-Anon meeting that I sure wouldn't call it one.
I have no idea how to stop it ............................ other than to look her in the eye, when she starts her 'rant' at you and say "NOT YOUR PROBLEM." Then ignore her.
J M H O
Love and hugs,