In your opinion, what is a healthy weight for a girl of 5'6? In your opinion, not what all these charts say, roughly how much should a girl with a height of around 5 6 weigh ? My little sister weighs around 100 lbs and think that she is fat. I think that she is far too skinny. She used to weigh about 120, but then she started starving herself in order to loose weight. Thankfully she is over that stage now, but i still think that she is very underweight . She knows all that there is to know about nutrition , but she chooses not to listen. Not long ago, she was eating no more then 700 calories a day ! Sometimes less then 600. Even though she has started eating properly now, she is still only 100 lbs. I thought she was slim when she was 120, but 100 is just ridiculous.