Complex sentence: As time goes on however, Gisselle, jealous of Ruby's friendship with Abby, exposes her has a quadroon at the school's Halloween dance, a secret Abby had been keeping in order to enroll at Greenwood.
Split into simpler sentences: As time goes on however, Giselle becomes jealous of Ruby's friendship with Abby. She exposes Abby as a quadroon at the school's Halloween dance, a secret Abby had been keeping in order to study at Greenwood.