Hello, 25years old male, girlfriend 22 years old. Dating 2 years and 8 months

Ill try to make this short. But my girlfriend has been pretty hidden about what she talks to one of her female friend "Roxanne".

Last night she left her computer open and i decided to sneak and see i know it's non of my business! But they both spend some time together, girlfriend goes to clubs maybe 2x a month, drive around the town 4-5x times a month with Roxanne. But like most girls do they talk about guys and other girls. (awalt)

But what i saw is that apperantly they know this guy "Chad Thundercock" which Roxanne knows better then my Girlfriend. But what i saw in the chat between them was this they where talking about him apperantly.

Roxanne: well Chad does have a nice body and nice dressing style!

Girlfriend: yeah he does.

Roxanne: Would you fuck him?

Girlfriend: Yes i would lol.

Roxanne: Why don't you?

Girlfriend: I have a boyfriend!

Roxanne: So? He wouldn't find out haha.

Girlfriend: Hehe. Maybe

Roxanne: I doubt it.. mine never did.

Girlfriend: heheh :p

This was it, but nothing else came the next subject was an hour later saying..

Roxanne: Yeaaa, You got plans?

It's like something is missing..

What should i do and feel about this? Normally i dont feel this insecure but having her female friend pressing on her to cheat on me hurts badly!