Allie watching Hannah and Garrett

During one of my many rewatches, I noticed a small but interesting detail. In episode 2, Allie watches Hannah and Garrett teasing each other and just stands there with a little smile on her face.

Do you think she already had a feeling that something could happen between them?

I also got the impression that, in that moment, she realized their "fake" relationship had more spark than her own two-year relationship with Sean. Maybe that was even part of what pushed her to go to the party... the party where a completely different story started to unfold.