I picture Mary in this scene, when Jesus says, "Not now, Ma!" having a knowing smile on her face, as if she's used to Jesus saying something like that before he goes and does as he's asked. Then she tells the servants, "Do whatever he tells you." She seems to know he'll do as asked and she knows she needn't know how it's done because she leaves the scene after saying that. She probably knows her son doesn't need anyone breathing down his neck.