I was guessing correct somewhat. They are having some marital difficulties and needed me to counsel them. But the topic I'm interested in came up and I tried to carefully avoid it. I am of course paraphrasing, and this wasn't a conversation that happened over a meal, it was days of back and forth:

Dad: "We noticed you and [LGF] are really getting along well, hmm?"
Me: "Yeah, we play all sorts of games, it's fun, your daughter has quite an imagination"
Dad: "Aren't you taking it too far? She tells me..."
Mom: [interrupting] "She loves you the most!"
Dad: "Yes, she loves you more than her parents. Why?"
Me: ¯\_(ツ)_/¯

Dad: [LGF] wants to go to your place tomorrow. We do not need a babysitter, you know?
Me: Oh, I know, but she is welcome to come by anytime she wants; of course, if that is okay with you.
Mom: [in background] why would she want that?
Me: [semi-silent] because she likes me, you old wench.

I could go on and bore you but we are fine. Right now.