The couple -- who's mostly kept their relationship under wraps in recent months -- drew eyes at Coachella's sister event Friday night ... swaying softly in a VIP area while Jelly Roll belted out some tunes.

Check out the clip ... MF and MGK don't move a ton, but they're definitely vibing with the music -- and, it looks like Kelly's even serenading Fox with the song adding to the romance.

BTW ... the loved-up dance is actually happening to a rather tragic song -- 'cause it sounds like Jelly Roll's "Save Me," which is all about him telling people in his life to get away because he's a broken man. Not the typical song to get one in the mood, but to each their own we suppose.

Now, as for what this means in their relationship ... quite frankly, we just don't know. Fox's last comments on her status with MGK hinted they're still together but no longer engaged.

Remember ... Meg went on the "Call Her Daddy" podcast last month and talked about her relationship with the rapper/singer -- calling him her "twin soul" while cryptically tossing out a "no comment" or two here and there ... really confusing fans.

This new clip seems to suggest they're still very much an item ... and, a pic of them hanging out on his birthday earlier this week also fans the flames.

Remember ... MGK posted a pic of them together on his 34th birthday, shocking fans who thought they weren't together anymore -- so, they're clearly still quite close