Eeesh. I'm not gonna call this one, but if in a year's time you realize that she's picked off your entire support one by one and Dave was just the first to fall, maybe don't marry her.

Also I think it's possible that Dave and Saf have some stuff going on that you don't know about.

You don't have to burn bridges here. Take time to work out your relationship with your girlfriend by telling Dave you need a bit of space and time; it's really normal for people who have known each other for that long to have had periods where they're apart.

Maybe they just hate each other. That doesn't always work out badly. Take me and my best friend's husband; we did NOT get along at first. But 15 years later we're really good at small talk.

Just take some space, get your head together, sleep, eat, think; don't rush anything, don't say anything you can't take back. We have to be most patient with our oldest friends, sometimes.