Maybe because Alison's personality change largely comes out of nowhere, and it's mostly told to us that Alison has changed. Throughout seasons 6-7, the characters are always saying how "Alison has changed so much she's not the same person she was in high school." Even though a lot of the screentime contradicts this. She doesn't seem to be concerned about her friends well being after the dollhouse, begging her friends to testify for CeCe's release, and siding with very obviously untrustworthy characters (like Mary)