How do I convince my girlfriend that even just sleeping in the same bed with other guys is bad?

Anonymous
hi so my girlfriend met up with an old friend today who's on leave from the military for two weeks and so she offered to let him stay over for three whole nights and when I asked where he was going to sleep she said her room, I asked her not to, to put him somewhere else but she insisted then when I asked her what was he going to sleep on she said her bed with her, but that it was just sleep, I begged her not to do that, not to sleep in the same bed as him since she has a boyfriend, me, but she didn't see what the big deal was, it was only sleep, when kept asking her she got mad because she thought I thought something was going to happen between them but I no that wont, I still don't want her sleeping in the same bed with him tho, help, how can I make her see even sleeping in the same bed as him is wrong?
Updates
+1 y
um from the rsponses I feel I should tell you guys this is a long distance relationship so going over there and sleeping there too is something I can't exactly do
Updates
+1 y
ok so she slept with him last night but we talked this morning and she agreed not to do it anymore, not to sleep with any other guys in the same bed, but now she's pissed at me for not being OK with it, and thinks I'm selfish now
Updates
+1 y
I officially don't like the friend now, while my girlfriend was in the shower he took her cell and texted me asking me to stop pissing her off, I tried to explain to him and asked him not to sleep in my gfs bed anymore but he replied no, if she lets him he's going2
Updates
+1 y
he went on to say stuff like how he doesn't want to threaten me or argue with me he just wants me to stop doing stuff to make his stay there worse, somehow he's making me sound like the bad guy here, I don't like it
How do I convince my girlfriend that even just sleeping in the same bed with other guys is bad?
19 Opinion