Grandmadonna 

a person of an elder age group who thinks they are as relevant as a younger, more-talented person.

Lady Gaga is popular today. Enough of Grandmadonna trying to claim she wrote all songs.

Grandmadonna by sesmith70 March 6, 2012

grammadonna 

A prima donna over 50, usually with one or more grandchildren. Usually requires a lot of maintenance and upkeep by a whooped, hard-working man.

Phyllis is such a grammadonna, she's making her husband buy them a million dollar retirement home in Costa Rica.

grammadonna by lamkaens February 19, 2011