Vegeta's away long enough to miss whatever she's been going on about with Yondu, so maybe he would have a bit more sympathy for her wanting to drink if he had heard her. A bit more. Not a lot. Not when he has to put up with her like this after this all.

He returns back to them not too long later, holding out a new cup for her, "Drink this." Handing it over without telling her it was water rather than anything else.