I've been in group therapy, and friendships/conversations about your problems outside therapy were highly discouraged/frowned upon.
I had the luck that I carpooled with a guy to therapy, and we got on together very well, so we talked a lot about the group.
We got repremanded often, but ignored that, we had fun, got better and moved on.
Many of the people from our group got stuck in a rut because they didn't talk to others about the group and therapy.
We basically got each other through it.
We don't see each other often, but when we do, we have a lot of fun, and we understand each other very well.
Even if it's not encouraged, I'd say try to find at least one person you click with, and if you both feel like it, meet outside therapy.
It just helps to have a support system like that.
If someone isn't in therapy or never has been, they won't understand you like someone from your group does.
And if your therapists really do mind a lot, try to find someone from a different group.
You can share experiences, but it wouldn't interfere with getting well.
Good luck! <3