Mrs. Morbucks is the mother of Princess Morbucks. Her only connection to the show is in the episode Boy Toys where Princess ends a phone call by saying to herself "Man, my mom can be such a pain in the butt".

There has never been implied any evidence of her existence throughout the entire series besides the mentioning of her in Boy Toys. She has never been seen with Princess nor Mr. Morbucks.

Powerpuff Girls Z

In the Powerpuff Girls Z series, Princess's mom does appear on the show and speaks.
Ppgz tv0254 resizer

Princess's mother in the PPGZ series.