The model was spotted out in the crowd while BB hit the main stage a little before midnight ... and she had a great view of his performance while surrounded by friends (and bodyguards). As you can see ... KJ was feeling the tunes, including the up-tempo salsa part!

Kendall did a little twist in line with the beat, so it seems she might've learned a new step or two while dating the reggaeton star ... whom she's been with, publicly, for 2 months now.

That's not all Kendall was into during the show ... looks like she got herself into a conga line, of sorts, while BB continued to do his thing. There was a huge smile on her face as she clutched to a pal of hers -- and she certainly didn't care that people noticed her either.

We shoulda figured Kendall would be here to support Bad Bunny -- fact is, they're kinda inseparable lately ... and their relationship is going more public by the day ... and there's nothing more high visibility than Coachella.

This also speaks to the fact that Kendall and Bad Bunny are, in fact, the real deal -- something that's been signaled for a while now ... especially with their recent intimate date.

BB is scheduled to return to Coachella for weekend 2, so it'll be interesting to see if Kendall makes it back here in 7 days to watch her man again. Something tells us ... she just might.