Maybe she can give you referrals to other groups in the community since it sounds like there are no options for you at the same place. Since she's new, she may not know the community well, so maybe asking someone else there for referrals (her supervisor?) might also be helpful.

It does sound like a worthless experience. I work at a place where some clients are very disruptive and it can be so hard to manage those people and still provide a helpful experience to the others. It sounds like your group leader needs a lot more support with this group than she is getting.

JMO, but the group sounds too big. 8 people would probably be better than 15. 15 is a lot to take on for just one therapist, especially when there are behavioral problems. If you do look for another group, a good question would be how large is the group?