Thanks for the query to H.C.M.Forum.
Liver function tests are normal including major tests .
Normal amount of albumin
is 35-55 gm/ L.
In your sister it is 18 gm/liter.
Protein is also passing in the urine as shown +++ ( this is also a type of albumin).
Now main cause of generalized edema is HYPOPROTENAEMIA ( HYPOALBUMINAEMIA ) .
Mal-absorption is one most prominent cause.
As you mentioned that she was a patient of hypertension
, so diagnosis is somewhat clear that may be, Chronic renal failure
So consult a physician and get his opinion along urologist
Hope I have answered your question.
If further any question I will help.