Not quite. If you calculate the Basal Metabolic Rate with a little exercise, her BMR at 500# is 4,066 calories (female, 5'3"). However, it decreases as her weight decreases. For 400#, it is 3,442, at 300#, it is 2,819, at 200#, it is 2,195. I calculated using a linear formula and for her to lose weight to 450# (50 pounds), at 1,500 calories per day, it would take her 2 months 10 days, and 2 months 28 days at 2,000 calories. To reach her goal of 175 pounds by following this diet, it would take her 27 months (2 years, 3 months) at 1,500 calories or 53 months (4 years 5 months) at 2,000 calories.Off-topic but I calculated how much weight she would lose if she fasted for a month and she would be down 160-170 pounds in 30 days.
Idk if you can legally pay to get fed through an IV but if she does that (and it ranges from 2000-1500 cal a day) she would be at her ultimate goal weight (170) in less than 6 months.
How many believe that she can maintain a 2,000 calories diet for over 4 years? I do not. Heck, she could not maintain it for one week.