Nanna pays a visit in Grandmommie Dearest, bringing chaos into the Bower/Micelli household... But, is this episode really plausible? Mona's mother had never been mentioned before, leading most to believe she was dead. Also, Marian Seldes, the actress who played Nanna, is only six years older than Katherine Helmond. The idea of her being Mona's mother could be pulled off, but only if she looked older.