People talking like Prez is confident, when really she's just too sincere for her own good. Seriously, the girls help each other almost more often than they make any actual moves themselves. At the end of the day they're all in love with the MC, but want to make sure the MC is happy and that none of their friends end up regretting unspoken feelings.
.....So yeah this is absolutely having either an open ending or alt routes for each girl.
Also, poor big sis. Brain scrambled because a new door's been opened and now she has to grapple with seeing their dynamic in a whole new light.