Not seen afterwards of episodes
After Zoey moves to England to attend Covington Preparatory School in "Goodbye Zoey," Chase, feeling guilty over how a lack of communication on his part was a factor in Zoey leaving, befriended Gretchen, whom he shared a class with, to fill the void.
Gretchen joins the gang for their usual volleyball game, proving a terrible participant, after which Quinn explains to Lola that Chase only tolerates Gretchen because of how much she looks like Zoey. She later joins them for a lunch, disgusting the girls, along with Michael and Logan, by randomly taking a bite out of Quinn's apple and then sticking her gum on the apple.
Michael and Logan later forced Chase to admit that he loves and misses Zoey and is only using Gretchen to fill the void. Chase presumably ended their friendship when he left for England to be with Zoey with Gretchen's personality not enticing the gang to keep in contact with her.
Despite the similar appearances, Gretchen is Zoey's exact opposite. Quinn summarized her as "nauseating" much to Lola's approval.
While Zoey is proper, Gretchen is seen doing various disgusting things, including digging in her nose, scratching her armpits, spitting, and popping her zits at lunch. Where Zoey is polite and considerate, Gretchen is rude such as randomly taking a bite out of Quinn's apple, grossing out Lola, Quinn, Michael, and Logan. In contrast to Zoey's independence, Gretchen seems rather passive, going along with whatever Chase desires and taking no part in the gang's volleyball game.