In "The Seinfeld Chronicles", Claire was a friend of Jerry and George who worked at Pete's. Here, she picked on George about him worrying about coffee. After this scene, she is not shown again in the episode. Claire is never seen or mentioned in any other episode of the series. Plus, Pete's is also never seen again, replaced by Monk's Cafe.
Notes About Nothing
Claire was going to be the female character of the show. She was ultimately replaced by Elaine after the series was picked up for a full season.