Episode 38 of "Sabrina, the teenage witch"
s02e14 Five Easy Pieces Of Libby

Mrs. Quick assigns Sabrina and Libby to decorate the "Democracy Day" float together, but Libby's obnoxiousness causes Sabrina to cast a spell keeping her a safe distance from Sabrina. The Quizmaster intervenes, blowing the whistle on an illegal use of magic to solve problems, and reverses the spell so that Sabrina must stick to Libby like unwanted glue. When a desperate Sabrina struggles free, the spell has disastrous consequences: Libby is transformed into an incomplete jigsaw puzzle, and Sabrina has only a few hours to locate the missing pieces and put Libby together again. This necessitates a visit to Libby's home, where her cold, controlling mother makes Sabrina understand her nemesis a little better -- as does the discovery that Libby has an ailing grandmother to whom she is devoted. Meanwhile, Zelda tries to find a miracle cure for disease but winds up inventing a miracle cleaning fluid which Salem and Hilda promptly steal and market in the Other Realm, oblivious to the unfortunate side effects of the magical brew.