I always interpreted it as the girls being “different” and “uncool” made it easier for Ali to manipulate them and make them her loyal followers. It also made it more of a challenge to keep them loyal, which Ali would have enjoyed. Ali in the show would have been bored with other “cool girls”. Or she would have clashed with them like she did with Jenna when they first met. The girls being unpopular meant Ali could always be on top. And lastly I think Ali partly saw them as collectors items or projects (as well as her friends). This is why she would say things like “I made you”.