Mean Girls 2
After they've had enough of all the terrible things that Mandi and her sidekicks did to them over the past several weeks, Jo formed a new group, which included Abby, Quinn, along with several other unnamed female characters.
The group quickly became popular around school, and Jo, as it's leader, was starting to befriend other students, leaving Abby behind. As time went by, Abby noticed that the popularity changed Jo, and that she's starting to become more and more like her nemesis, Mandi.
Soon after, when Abby found out that her father paid Jo to be friends with her, she furiously left the group along with other members, disappointed by Jo's actions.
However, later in the movie, they all reunite once again on the school's football field to finish off the Plastics once and for all. Afterwards, the group disbanded, as with Mandi gone, the Plastics weren't posing a threat anymore.