However, the other Slytherin’s believe she did it because Draco was really annoying and are inspired to do the same.
Lots of the former Slytherin’s get re-sorted into Ravenclaw or Hufflepuff instead.
Soon enough Draco is basically the only Slytherin left. Even Crabbe and Goyle got re-sorted, somehow getting into Ravenclaw. Pansy went into Hufflepuff, whilst Tracey and Astoria followed Daphne into Gryffindor.
(Daphne decided she had to be re-sorted as being in Slytherin meant that other Slytherin’s would try to interfere in her relationship with Harry)
No way Crabbe and Goyle get into Ravenclaw. Also, who is Tracey?
Tracey Davis.
She’s not mentioned in the books, but she is in Rowling’s notes, where we learn that she is a Slytherin halfblood in Harry’s year.
https://www.reddit.com/r/HPfanfiction/comments/iwj9ep/tracey_davis_halfblood/
https://www.reddit.com/r/HPfanfiction/comments/rbda51/is_tracy_davies_a_canon_character/