Starting MC Day 1 Monday - possible to lose too much weight? Gallbladder removed?

I'm starting The Master Cleanse with my sister and her husband. He's doing it to quite smoking and we are doing it for general cleansing. I would like to lose some weight and keep it off. However my sister doesn't need to lose any weight and we are concerned that maybe she is too skinny to do the cleanse for the full 10 days. Is this possible that she might need to quite if she loses too much weight?

Another question I had my gallbladder removed a few months ago. Do I need to worry about anything?

How much exercise should we do while on the cleanse?

That's all for now :)
THANKS!!!