Sabrina is introduced to Gwen as her roommate when she travels to Rome. Sabrina is worried about having a roommate (since she hasn't yet learned to completely control her levitation while she sleeps), but is happy to discover that Gwen is a fellow witch. Gwen is exposed to Sabrina when her guinea-pig Stoney begins to talk. Gwen has a hard time controlling her magic and often when she tries to freeze time, she ends up splashing water over people and when she tries to transport herself, she often ends up in Greenland and says 'frizzle'when ever she get a spell wrong. Gwen falls for Alberto and accidentally turns him into a pigeon when attempting a love spell. It is later revealed that Gwen's affection is reciprocated. Gwen helps Sabrina to track down the secret to opening her aunt Sophia's magic locket. When Gwen discovers that Paul was trying to set Sabrina up, an angry Gwen attempts to transform him into a goat as punishment, but accidentally turns Alberto into a goat.
Gwen is invited by Sabrina on her trip to Australia. It is revealed that has a little brother called Arthur whom she turned into a tree. Gwen's magic has improved since her trip to Rome, however she is still quite clumsy with her spells, but manages to magically transport herself and Sabrina back to their room perfectly (however, she later zaps herself into the sea when attempting to reach a boat). Gwen also turns Salem into a fish when trying to conjure a dolphin.
Gwen's magic manifests as green sparkles which either radiate from the contours of her target, or shroud her target. She activates her magic by clenching her fist or closing her eyes tightly; usually both at once..