Well, they were still dating in PoA, so I think it would make sense for them to break up during GoF, or the summer before this book. In this time period, Percy is really getting more job-oriented than relationship-oriented (family or otherwise). I think his ambition wasn't so prominent in his school years. I don't picture him and Penelope maintaining any sort of relationship after that. Percy is very high-and-mighty, and I could see him looking down on his "youthful years" when he was just a schoolboy and dating Penelope. I think when he sees the relationship in retrospect, he won't think it was very serious. She definitely wouldn't have met his wife--Percy's marriage takes place after his character has changed so much(for the better) and I think he would be the type to move forward, not backwards.
Also, when do you think she and Percy broke up? When they were still at school or after they graduated? Would it still be a cordial relationship or a bit embittered? Do you think she and Audrey knew each other first, and that's how Percy met his wife?