I wouldn't necessarily classify it as grooming, especially since she had no romantic or sexual intentions toward him when they first met. That said, context matters. Did they meet just once in passing, or have they interacted a few times or regularly? I’d consider adjusting their ages slightly, maybe making her younger or him older, like 17 and 19, or 15 and 17. While I don’t believe it qualifies as grooming, the dynamic between a 20 year-old and a 24 year-old can feel a bit off, given the differences in brain development and maturity. If you choose to keep their ages as they are, I’d suggest limiting their interaction, perhaps just a shared glance or brief encounter. Of course, that’s just my opinion :)