Rosenthal was still indoors and relatively nearby the others. It's not like she went strolling alone outside among the deadgineers at night. Now that would have been a full blown horror cliche. Also, David was not some total stranger. They knew he was from the crew of the Prometheus; a supposed ally.
Prometheus and Covenant are not irreconcilable with the introduction of David as the progenitor of the Alien, and I think Covenant should be commended for how it addressed the effects of the accelerant without getting bogged down or making things worse. It certainly did a better job of explaining it than Prometheus did.
I think it will be at least a year or two down the road before Fox has serious considerations on a sequel to Covenant due to the lackluster performance at the B.O. It would be entertaining to see what happens next, though I'd be content if Covenant ends up being the last of the prequels.