Complex sentence: At the end of the episode, Cher and Sabrina walk out of a building together and Cher seems confused that Sabrina has allegedly gone to her school since September of that year and that she had never seen Sabrina before even though she (Cher) knows everyone.
Split into simpler sentences: At the end of the episode, Cher and Sabrina walk out of a building together and Cher seems confused that Sabrina has allegedly gone to her school since September of that year. Cher had never seen Sabrina before even though she (Cher) knows everyone.