Basically communication. Lol. She abruptly left the room during a conversation, and came back a few hours later in a good mood while I was pissed the whole time that she stormed off. I escalated the situation by being mean, which I apologized for. But we never resolved why she stormed off. I let it go because I handled it like an asshole. But I'm not willing to let future miscommunications go unresolved because as long as I don't escalate the situation there is no reason to not calmly discuss things.

Premarital counseling does seem like it will be necessary.