Groot's not entirely sure what that look is about, but he's having fun dancing alongside someone as enthusiastic and free as himself. Her motions are more aggressive than Quill's, full of energy and passion in ways that don't involve quite as much hips, and that speaks to him in ways that Quill's 'pelvic sorcery' never has.

"I am Groot!" He's shown you his style, now time to learn from hers! Lead the way, Jaylah. There are so many new ways to dance that he has to learn, and where else is he going to find them? Drax? As if.