I'm mostly on the American Cockatiel Society. The National Cockatiel Society has a lot more activity so you might like that. Those are the two I belong to but there are a lot of other cockatiel groups too. I don't know how many there are because the Facebook search function seems pretty limited and it'll only show about six at a time. Maybe somebody who's more Facebook-savvy can tell me how to find more. If you want a group that Susanne belongs to, here's one:
https://www.facebook.com/groups/cockatielforum/ I don't know whether she's active in it though.