Question: This might be a stupid question, but why did Roxy not show up the town? Was it really just "circumstances beyond her control"?
Continuity mistake: When Dinky falls to the school bus floor, then gets off the bus, there is a smudge/smear of something grey on her cheek. After Gerald chases her and tackles her to the ground, the smear is much larger. Her cheek never hits the ground in a way that would make a bigger smear.
Dinky Bossetti: Who understands ANYONE these days... who WANTS to?
Gerald Howells: Gosh, I want to kiss you so bad, Dinky.
Dinky Bossetti: It's good to want things.
Answer: My interpretation is that Roxy had always been determined to get away from the town, and pursue a life of wealth and fame. Attending the event would mean visiting the past that she wanted to forget. She was too afraid to go through with it.