what about the unhealthily fat
I do think there is an issue with overweight becoming so normalised that people fail to understand what normal is. However, being overweight is not something that young girls aspire to, and seeing one overweight celebrity is vanishingly unlikely to change their perception of what is a normal/desirable weight.
In contrast, young girls DO aspire to look as thin as the women they admire on television. And as someone said above, while a person who is a couple of stone overweight may be harming their long-term health, a person who is two stone underweight may be at risk of much more immediate and more serious health consequences.
In addition, many women who maintain very low and physiologically inappropriate body weights do so by abusing drugs or by vomiting or by binge-restrict eating habits - all behaviours that have serious health consequences in addition to the health risks of being excessively thin.