Help me with my best friend.

Shalom

my bestie from a real young age, lets call her W. So W is dating this guy, G. Well G is a flirt towards most girls he talks to and I didn't understand her when she would be very angry at him. Well we three were on a camping trip and when she wasn't around, he, at first, would talk about their relationship. But the more he was around me, the more he flirt. So before this becomes to long, long story short, he touched my boobs ( I didn't know how-to react to this. We we're talking about how W is border line anorexic and he said he wished she was my size), complemented my body multiple times (saying it was perfect), and then admitted to last time we hung out, he wanted to kiss and then asked to rate my kissing skills. I declined and insisted on a boundary. I am in a serious relationship of 2 years and we've already had our issues and are just starting to be a real good couple. I'm planning on telling W that all this happened, with encouragement from my parter and other bestie. what do I say?