You sound like such a lovely and gracious person. But seriously, you shouldn't feel bad. I would feel bad for Maddy if it was her parents talking her up and she just went along with it, because I've been there. My MIL speaks a notoriously difficult language and I made sure to learn a few common phrases before the first time I met her, along with trying to learn the language in general. She was absolutely tickled by that and kept telling people I was fluent, even though I still am far from fluent and it's been a long time. She's a lovely woman and never meant any harm, but it put me on the spot a few times when people spoke to me in that language and I had to explain that no, she was just really happy I was showing an interest, and I actually have no idea what they're saying. Sometimes when she'd describe me as fluent at parties or whatever, though, I wouldn't correct her in the moment because I didn't want to embarrass her. I'd just say something noncommittal like, "Oh, MIL, you give me too much credit!" and then either my husband or I would clear it up later if it was someone we saw a lot.

But that doesn't sound like what happened with Maddy. She was basically inviting people to engage with her by saying she wished she had someone to speak in those languages with. And those aren't even uncommon languages! If I were you, I'd be laughing along with Jake and his friends.*

*actually, I'd probably feel bad too because I never like seeing people embarrassed, but I still think she brought it on herself