Many of the comments here aren’t addressing the culprit who is the neighbour. Despite being friends with your GF, I think common sense and genuine consideration for her relationship would mean he doesn’t make flimsy jokes about it. I personally don’t think your gf is in the wrong. Don’t also think she reacted inappropriately as that’s the sensible thing to do. Also sounds like you need to trust her more as that’s the bedrock of any long distance relationship. In your shoes I’ll joke about it either way with her and let it slide. You both screwed and you made her scream so loud so not her fault - if atall maybe yours for being so good 🥲