It's not an easy decision— not one lightly made. It's just that her track record at weddings sucks— in a manner of speaking— and even though she is comfortably ensconced with Puck, who was trained by the best— incidentally— and who is so often elsewhere— happily— and who will be there, whether or not she is, the whole Brittana wedding thing is making her itch.
Which— it's just as well, anyway— she has double rehearsals all week, and she can't let her cast down, and there aren't valid excuses in theatre, and without her— well, the show will go on, just without her.
Quinn still figures that their thing— which wasn't even a thing— more of a fling— or a dabbling— or a—
She needs not to go there.
Because she needs not to go. She needs not to see Santana pretending nothing happened, and she needs not to have Brittany give her the "who-is-the-new-kid-with-the-Afro" look.
Fuck it.
Puck will fly in and defend her. Puck will be there without her. Puck will give her greetings and blessings to them better than she ever could.