How thin is thin for girls?

I watched a programme talking about his girl is about 160 cm and 50 kg and said that she does not concern her weight so indicating that she thinks she is a bit fat.

I noticed that the younger girls (30 years old or below) from my country are mostly 160~165 cm height and 42~48 kg but for girls over 45 kg, they will try to get their weight under 45 kg.

I live in the UK at the moment and there is a girl that is 42 kg, about 163cm (she said she is 42kg, don’t know the truth). For a white English girl, other women in my office think she is crazy thin.

However, that sort of number for me is just amazing. I am a guy with 105 kg, 185cm. I am twice of their size and so many guys in my office are bigger than me.

Do you think a lot of women are pursuing ‘under weight’ than normal and they are too thin? The girl I was talking about with 42kg looks great and not too thin at alll but she is a good dresser. Dresses can make appearances change a lot. I personally think girls with some weight on and a bit more curvy is better.