This is more of a Ben/Biao question and the patient is CURRENTLY vomiting for one week. That needs to be stopped first, so that is why that is the answer. Yang Deficiency is likely the root and can be treated after.
Anytime you see “Water Fluids” or “Fluid Retention” this just means there is an accumulation of Water as opposed to Dampness or Phlegm. Read: less sticky or cloying, but can still impair bodily functions. Your job is to Drain it – no different than Dampness.