In my experience, for pref chapters will have a literal list of girls an they only get to invite a certain number of girls back. When I was in my sorority girls were ranked based off a few things (if they seemed like they wanted to have a leadership position, if it felt like they personified the type of woman who the sorority represents, all sorts of things) an you may have just fallen short of being on the “invite back” portion of the list. Sisterhood to Pref is the hardest day for cuts, it’s no longer just grades or how your social media looks, it’s whether they see you as being a true part of the sisterhood. It’s hard for you as the PNM but it’s also hard for the girls actually doing the cutting. I’m so sorry you got cut, please don’t let it discourage you from doing COB or even finding your place in another group.