instead of worrying about theoretical possibilities. worry about what you can and can't do and will happen depending on how you choose.
there are two things you can do.
first, you can approve of this relationship. and risk a possibility that she might cheat on you with him. however, keep in mind, she could cheat on you at any time and with any person. so...something to think about.
or
second, you can disapprove of this relationship, and she will resent you and see you as an AFC.
it's your choice, but make no mistake, those ARE your choices.
if it makes you feel any better. i was best friends with a girl from age 18 to 20. and she was a smoking hottie, but i was a total AFC, there were so many times she could have initiated something. we were alone on so many occasions, even in her bedroom. she never did anything. so, yes, there are girls out there who genuinely can have a guy friend and never do anything with him.
now, on the flip side, you KNOW this dude wants to bone your girlfriend. because guys don't have girl (space) friends and NOT want to fuck them.
it's a sticky situation, but so is life.
if he really sets off your creep alarm, maybe you need to gently "scare" him away when she isn't looking. so what if he comes to her about it, deny, deny, deny, make him look like a jealous clinger.
