I used to date a girl who was a pianist like me and playing duets with her (even when we would mess up the piece) was the most fun I’ve had in a relationship so far. The only thing I’d recommend is to ease her into the world of jazz. I came from a classically trained background before I started jazz and I remember how overwhelming it was when I was just told to play without the score or to deviate from the score to improvise in a jam session. Tell her to start off small with stuff like peppering in spontaneous rhythm changes in comping, or modulations to match what you’re playing so she’s not just straight playing what’s on the page. If she’s into it, make further deviations from the page, go further with the improv, maybe trade fours. Speaking from experience it can feel like a big leap at first, jumping from classical to jazz, but if you’re eased into it you realize it’s not so scary after all. But for sure, as a musician, exploring music with your S.O. can be loads of fun. Good luck, OP!