How are you are your sister now? Protiens in urine can be due to three reasons:
1: disease of the glomerular system
2: high intake of proteins
3: inability to reabsorb proteins (fanconi syndrome
From what i understand your sister has 1 or 2. I will try to explain both of these conditions to you.
Fanconi syndrome can be inherited that is it runs in your family or acquired by the use of medicines. please discuss all the details of any medicines your sister is using with your doctor. Mainstay of treatment for this is replacing what the body is loosing that is fluids and bicarbonates mainly.
is a vast subject. You would have to discuss this with the doctor who is treating you sister. Categorize the type of disease she is having and treat accordingly.
High blood pressure
is also a risk factor for developing loss of proteins in the urine.
Do not worry most of the diseases which come into these category are treatable. and we can slow down the disease process by controlling the blood pressures.
I hope your sister a speedy recovery.