A character's introduction is often crucial to how they are perceived for the rest of the series.
Sam had this same problem, in the first few episodes she was fucking up the school lunch menu with her vegan bullshit or generally just being a bitch. Even though she became better as the series progressed, a lot of fans never really were able to look past her initial bad characterization and thus preferred to ship Danny with the niggress or latino chick instead.
Conversely, the two other FOP girls had good introductions. Tootie was highly sympathetic in spite of her flaws, Trixie may have been bitchy but she showed a soft side. As the series went on, Trixie became more of a vapid slut, but still retained a good amount of people willing to ship her with Timmy no matter how much the series pounded you on the head it was a bad idea.
Kitty Katswell and Darcy are also Hartman sidekick girls that were generally entertaining, if flawed in some way, and were thus found to be likable from the get go.
Chloe was a character who the show was trying to sell to the viewer too hard, and it led to backlash. She occupied a slot already covered by other characters, and although Kari put a lot of heart into the character, the poor writing surrounding her and fact she was usurping the roles of Timmy and in some ways Tootie simply led to her being scorned. The writing of the show just sucks now all around, it isn't funny at all, the same characters appear way too fucking much (Crocker and Timmy's Dad mainly), and the plots are just generally uninteresting, even that episode with Vicky that was linked above was basically "Vicky torments kids again, except now Chloe is there".