So my friend needs some advice?

my friend dj is hanging out with this guy garret. garret has a girlfriend named michelle. but garret and dj always hang out and are both aware that they like each other. michelle and dj are very good friends. garret doesnt really mind if he dates both of them at the same time. dj doesnt feel completly comfortable about it but she suposly loves him. michelle has no idea about what is going on between them. ADVICE??