Hi - I had the same problem around the same time. My doctor had me on 1000 to 1200 per day and I was not losing weight. I did some research and found that other doctors and nutritionists said that can happen if you are not eating enough calories for your activity level so I increased my calories to 1400 per day! I not only felt better i started dropping weight. I have been losing 3 pounds per week since I increased my calories. I am a very active person. I also make sure I have some kind of snack (focusing on protein) every 3 hours and I drink 50-64 oz ( I know that is light) of water per day. My surgery was on may 3rd, 2018 and I am down 43 lbs since April 17th when I started my liquid diet. That averages 3.9lbs per week.
i know it is strange to be able to eat so many calories and still lose weight. It's nice not being hungry! Best of luck to your family member.