Karel:
I agree that the protagonist wants to catch up on all the fun time she missed in high school.
So maybe something like:
When a high school overachiever discovers her party-animal peers also got into A-list colleges, she vows to cram four years of fun she missed into one night.
(27 words)
Although, technically her specific, concrete goal is to crash the graduation bash of the in-group -- all the party animals whom she has openly despised (but secretly, unconsciously envied). Except she doesn't know where the bash is being held.? Which takes her 1/2 the film to find out -- the MPR.?
But phrasing the logline that way falls short of? conveying the full sense of the film's theme and her objective desire (and subjective need).? And my philosophy is that the prime operative of a logline is to sell the sizzle, not tell the story.?
So...
?