History before The Freshman/Sophomore/Junior series
Kappa Phi Sigma was founded by a student named Trixie Cartwright decades ago. She was also presumably its first president. The sorority serves as a hub for many of the rich female students on campus, and many of its members hail from wealthy families.
When Trixie graduated from Hartfeld University and in-turn had to leave the sorority, she left behind a sweater of hers as memorabilia. It is mentioned by present-day member Madison Eckhart that Trixie has since passed away, indicating just how far back Kappa Phi Sigma's history goes.
History during The Freshman/Sophomore/Junior series
Presidency of Becca Davenport
It was established in The Freshman, Book 1, that Becca had been the sorority's president for some time. She proved to be a ruthless leader, especially when considering her harsh and incorrigible personality.
During The Freshman, Book 1, Kappa Phi Sigma hosted a rush week for prospective members from across campus. Among these potential members were Your Character, Kaitlyn Liao, and Abbie. The primary task of the competition was to find the late Trixie Cartwright's sweater, which was hidden somewhere throughout the university. After the hunt was completed, only Your Character, Kaitlyn, and Abbie were allowed to progress to the initiation stage; a game of Truth or Dare. After this was completed, Kaitlyn and Your Character (the latter is dependent on how well the player did during the hunt) were officially made members of the sorority, but Abbie was not. Once it became clear that Becca was trying to break up Your Character's friendships, as she had not liked her from the moment they met, both Your Character and Kaitlyn quit the sorority in solidarity with Abbie. It should be noted that if Your Character was selected to join Kappa Phi Sigma, all events in the story that take place after the competition treat Your Character as having never been a part of the sorority.
Under Becca, the sorority engineered an Alyssa Griffin concert at Hartfeld in support of Sebastian Delacroix's campaign for president of Hartfeld's student council during The Freshman, Book 2. The concert was extremely successful, but was derailed due to Your Character and her friends starting a snowball fight which quickly spread to include the attendees of the concert. Ultimately, the concert proved to have been done in vain as Sebastian's opponent and Becca's ex-boyfriend Chris Powell was elected as student body president.
Slowly but surely, Becca became more unpopular among the sorority, and by the time of The Sophomore, Book 1, she had been ousted following an election in which only one vote had been cast for her to remain president. She was replaced by her best friend Madison Eckhart, who she quickly became estranged from as she saw her replacement of her as a betrayal. When Becca's parents got divorced, it was revealed that her mother had signed a prenuptial agreement, leaving herself and her daughters, Becca and Alexis, without money. In the aftermath of this, Becca was kicked out of the sorority when she wasn't able to pay the fees anymore.
Presidency of Madison Eckhart
Madison was elected president of the sorority shortly before the events of The Sophomore, Book 1. Ironically, Madison was the only member of the sorority who had voted for Becca to remain president. Becca saw Madison's ascension to the presidency as a betrayal and their friendship broke down, causing Madison much grief. Despite this, she took to her new position well. At this time, the sorority gained new members as the new academic year started. New members included Claire Pierce and Chelsea McIntyre.
In The Sophomore, Book 2, Madison and Becca started to take steps to repair their friendship. It was at this point that Madison revealed she was unhappy as sorority president because she hated what it had done to her friendship with Becca. Subsequently, when Becca orchestrated a musical number on campus as a grand apology gesture to Madison, the pair finally made up and Madison resigned as sorority president. It's not known who succeeded her. It should be noted that Madison would've had to resign at the end of the academic year anyway, since she was due to graduate anyway.
Additionally, the sorority provided support to Chelsea when she was being harassed by her ex-boyfriend Manny De La Cruz. Chelsea eventually filed a complaint about Manny's behavior to the university's management with the support of Your Character and prompt action was taken against Manny.
Presidency of Chelsea McIntyre
When Madison graduated in The Sophomore, Book 2, it was initially unknown what happened to the presidency next. It can be assumed another election was called to select Madison's successor. Whatever the case, it was revealed early on in The Junior, Book 1 that Chelsea had become president of the sorority, as she had stated she planned for in The Sophomore, Book 2.
Bold letters indicate members who have been presidents of the sorority at one point since the events of The Freshman, Book 1.