Relationship vs friendship

well first of all I would start off with saying.. you and her have no reason NOT to trust him unless he has done something to betray it.. second.. talk to him about it.. don’t get all made, just casually bring it up.. and if you don’t want to do that..

then here are somethings that help figure it out

1. how does he look at her, does he look like he is really focusing, or kind of just nodding along
2. when he looks at her, does he kind of stare? if he does.. this means that he is kind of… deep in thought about her.. like “What could she be thinking right now.”
3. sometimes guys are really good friends with this one girl.. and sometimes they need that girl to casually flirt with in ways that he doesn’t want to flirt with you… (rudelike, TOO sexual)

last.. well I am not a man.. so I don’t know.. but I have to say.. put yourself in his shoes.. if you were a guy.. what would attract him to her.?

BUT MOSTLY OF ALL

guys are all different.. so you have to think about your guys overall attitude if he has done stuff with other girls, hooking up. (regularly) then make sure you talk to him

mainly just talk to him.. because it could all be a misunderstanding.. he could just be a flirt.. flirts with a lot of girls, but no action.. a lot of people are like that.. so just ask him what he thinks of her.. but yeah