Three years ago, I was on a trans Atlantic cruise and one day out of port it was announced that a handful of people on board (mostly crew) had NorvoVirus. The ship wasn't at quarantine levels, but they staff wanted to prevent an outbreak.
By announcing exactly what happens rather than "reassuring the public" people feel more like part of the solution and take appropriate measures themselves. Also, those who feel ill tend to self-isolate. Cruisers accepted restrictions without question.
Judging by this experience, I'd say that letting people know exactly what the situation is probably helped stem the possibility of a spread of disease.
Thank you for your reply. I guess we will find out if she is sick when the ship arrives on Sunday morning in Galveston.