ok at first the opening credits went like
Bea Arthur
Bill Macy
Adrienne Barbeau
Conraid Bain
Rue McClanahan
Esther Rolle

later in the seasons 1977-1978 or so
Bea Arthur
Bill Macy
Conraid Bain
Rue McClanahan
and
Adrienne Barbeau (sometimes she was on there )

what happend i guess her name only appeared if she appeared

Adrienne Barbeau only appeared occasionally during the last season (whether or not this was her choice, I don't know). In the episodes where she didn't appear, her name was deleted from the opening credits.