From ksitetv.com's latest interview with Shelley Hennig (Diana):
"The older generation of Chance Harbor seems to have secrets of their own, and we asked Shelley if she thinks Diana is on to the idea that her father is hiding things. "I'm sure. Even in the third episode 'Loner' you see Diana start to look at her dad like 'what's going on?' Maybe I'll believe you that you're dating my principal, maybe you're not. But I think we're all suspicious of our parents. There will be a lot of suspicion and surprises with the parents for sure," she says. And speaking of those surprises and secrets with the parents, what's coming for Diana and Charles? "There are a lot of father-daughter moments with Diana and her dad. I have really enjoyed shooting those with Gale," she says."
KSiteTV’s Vancouver Secret Circle Interviews, Part 1: Shelley Hennig (Diana) Speaks!