She is never soon, but mentioned often. In Starring Tracy Beaker, Tracy suggests Cam buys Penelope fake pearls for Christmas, but Cam rejects the idea, saying her mother, "would never even touch fake pearls," as she can't afford real ones (Cam.)
In The Dare Game, Tracy says that Cam's mother is "This weird old posh lady who lives in the country somewhere and doesn't want to see Cam anymore because she disapproves of her lifestyle.
Penelope appears in one episode in Series 4. Episode 4- Meet the Parent. She buys Tracy an X-Box, and buys Cam make-up. Only Tracy likes her present. At first she seems fun, but it wears off when she hogs the X-Box.