It actually depends on height. 176 pounds on 6ft Amazonian is indeed far from fat. But, 176 pounds for less than 5ft is overweight. You can't say it's not fat unless you know their heights.

I'm not trying to decline your opinion, but sometimes there is things that boy could not understand and vice versa.

I personally think she only want to slimmer down a bit, not to be underweight or skinny as bones. It's ok if she want to diet, as long as she not embrace pro Ana lifestyle or having any eating disorder.