Jen, I am not going to try to convince you to go to Al-Anon.
I would like to suggest that you go, by yourself, to 5 or 6 DIFFERENT meetings and just 'check it out.' You may be surprised that many of your 'preconceptions' are erroneous. See for yourself. See how different meetings are run. Listen, you don't have to share if you don't want. Pick up some of the literature. It really is not 'group therapy.'
It is struggling souls who have found or are finding a 'solution' for themselves. They share their individual Expeience, Strength, and Hope on how they are moving forward.
Won't hurt to just 'check it out for yourself.'
Then decide whether to attend one with your Sister In Law.
J M H O
Love and hugs,