Why does Howie, Greta's manager, keep in constant contact with her during the cruise in the novel, The Unsinkable Greta James?

Howie constantly communicates with Greta while she is on the cruise to talk to her about her upcoming performance at Gov Ball. In light of her recent public breakdown, Howie believes the Gov Ball stakes are high and wants Greta to be ready. He also communicates with Greta about the fake engagement announcement online. He tells Greta they can either kill the story or use to attract press for her upcoming show.