Ariana Grande Thinks Pete Davidson & Kate Beckinsale Make a Cute Couple

Ariana Grande is flashing a big thumbs-up over her ex, Pete Davidson, getting together with Kate Beckinsale -- but on the issue of backing out of the Grammys ... zip.

AG was leaving Westwood One Radio Networks late Wednesday night in Culver City and our photog asked if she thought Pete and Kate -- who's 20 years his senior -- make a good couple. It's a lot better than that. Ariana says they're, "So cute!!!"

PD and KB have been hangin' quite a bit lately, and recently left a theater together hand-in-hand. The new pairing doesn't seem to bother Ari one bit ... nothin' but love here.

And, not only for Pete ... you gotta see her interaction with our guy. Ariana introduced us to her mom and some of her pals. She still wasn't down to talk about her Grammys boycott -- reportedly because the show's producers won't let her perform "7 Rings."

But, there was one topic she was dying to discuss -- eats. Late-night eats. We've all been there.