is it sudden? iirc in beyond the enterprise is actually in the tail end of her five year mission at the start, so there's plenty of time for a falling out and separation of ways. although given it's explicitly an alternate universe, they don't *have* to, at least not to the degree they did in the "prime"...The crazy part is the sudden disappearance of Carol Marcus is repeated in the Kelvin movies between Into Darkness and Beyond. And as before, she's not even mentioned.