Talk to Bariatric Surgeon on Overweight

Hello. My mother's weight was around 100kg because of which she was facing several other medical issues. The doctors advised us to lose weight at any cost. I personally visited a nutritionist and dietician but they were of no help. I did some research and started a 1200 calories diet for her and with that she started walking too. She was able to lose more than 10kg in four months, her weight was 86 before Ramzaan started. We didn't follow the 1200 calories diet during Ramzaan and now she is back to 95 kg. Please advice if 1200 calories is sufficient for a person? And is it safe and healthy for long term? I also dont want her to count calories and eat for the rest of her life... Please suggest some other healthy diet options which she can follow to lose her weight. We need her to go back to 60-70kg so her health issues start getting better. She walks 6000 steps daily (divided in two parts) What other diet options are suggested?