Here's the thing: I don't think either of them are really at wrong for what they did as kids. Penelope was a starving slave and didn't want to ever go back to that life, and she said something horrible. But she was a child, children say horrible things without realizing it all the time. And Reynold at the time was also a child so I understand why he hated her so much then and why he framed her for the jewelry thing. It was a horrible thing to do but kids are horrible sometimes, that can be forgiven too.
However, Reynold is now an adult and its been 5+ years since that comment, the fact that he's held this grudge against an 11 year old for a shitty comment (when he KNEW she was a slave and picked off the street) makes him a bad person. I hate him. He has no empathy. I know this is an attempt for the author to somewhat justify Reynold's hatred of Penelope, but it's not working. He just looks like a petty idiot who never grew up.
