Olivia (voiced by Rini Bell) is a girl from Tom Landry Middle School introduced in season 12 episode "Bobby Rae". She does not seem to appear or even be mentioned in subsequent or prior episodes.
She is a reporter for the school paper who is impressed when Bobby protests the vending machines and gets them taken out of the school. Bobby feigns interest in her activism to spend time with her.
When she is upset by the advertisement of energy bars Bobby confronts the teachers again, and when one of them tells him not to do a walkout he is initially compliant (going with the suggestion of a school dance) until Olivia expresses her disappointment with Bobby's compromise.
This leads Bobby to go back in and declare a walkout, which the school follows.
Bobby tries to calm the protesters when they begin to attack shopkeepers and loot stores. Olivia initially seems on board, but then suggests burning down City Hall to make a point.
After Bobby leads them to Strickland Propane for help from Hank who disperses the crowd, Olivia dumps Bobby for his peaceful ways, going off with another boy.