Question on 1200 calories for us small folks

BMR is essential body functions only. You need to run a TDEE calculator, or just set MFP to a reasonable rate of loss (based on how much you have to lose) and choose an appropriate activity level (probably not sedentary, in other words).

If you choose sedentary and 2 pounds per week, you'll probably get 1200. Don't do that

Oh, to answer your question - the 1200 limit is there to help ensure you get adequate nutrition, including an appropriate amount of fat and protein, in addition to micronutrients.

Your BMR is the amount of calories your body would need to support basic bodily functions and nothing else. You don’t need to eat below your BMR to lose weight you need to eat below your TDEE which is your Total Daily Energy Expenditure and includes all your Daily activity and any purposeful exercise.

1200 is the minimum calorie recommendation for women to get adequate nutrition, and most women don’t need to go that low in order to lose.

As a wise rabbit used to say, the winner is the one who eats the most and still loses. Instead of asking if you can eat below the minimum calories you should be trying to figure out how to eat the most possible calories and still achieve your goals.