You need to find out your BMI - it's something like divide your height in cms squared by your weight in kilos squared. I am sure you could find a web page with a chart on. Low to mid 20's is a healthy weight. I am 5ft 5 (& a bit) and weigh 8 & half stone and take size 10 clothes. My BMI borders on the unhealthy but I am not skinny by any means.
Depends on your build. I don't think there is a right and wrong weight for someone, it just depends on how the individual feels about their own size and weight.
Hi tigger, I am the same height as you and am currently on a weight loss plan. My GP told me yesterday that the ideal weight at 5ft6 for a healthy BMI is anywhere between 8 stone 7 and 11 stone 7 depending on your build, so you are very slightly above the maximum recommended weight but nothing to worry about really. I am aiming for about 10 stone 7 cos I am a medium build, i'm always going to be curvy!