<human>: I'm friends with a guy, "John," who usually goes out on outings with us and another couple, including my friend, "Anna." John is reserved, shy and quiet. Anna can be boisterous and very playful. On our last several outings, I've noticed John being unusually aggressive toward Anna.

She was playing around with him at a dinner we had -- holding something out to him but not letting him get it. He sat there and glared at her until my husband intervened. I get it: that can be annoying if you don't know someone well or you're just not wired that way. She didn't do it for several minutes, for what it's worth.

There was a Facebook "event" page recently where things got really...bad. John made reference to something Anna didn't understand and was making fun of the way she spelled something. I don't think he was necessarily trying to be malicious, but hell, I don't even know anymore. She started teasing him in return, saying that he was being a spelling Nazi. And then he went off: "First off, this means (x). Secondly, why would you like a post you don't understand? Third, I deleted this post because you deleted your post, so the context was gone. Fourth..."

It was ugly. These are just a few instances, but now I'm afraid of having the two of them together at the same time. It's readily apparent they just don't get along or don't understand each other.

My husband is slower to pick up on tensions between other people. I've shared my concerns that this is going to escalate into something even bigger, but he shrugs it off.

Do I talk to them both separately? Always hang out with them separately now? I feel like Anna has thrown some stones, but John is dropping proverbial bombs.

I don't want to have a dinner that escalates into a blowout fight.

Give me the gist of the text in a nutshell
<bot>: One friend more outgoing/playful, other friend quiet. Don't get each other. Snapping at each other. What do I do?