It's a tricky one. Ultimately it's her choice, and it's good to redress our expectations of models.
However.
I don't think being that big, whatever gender or orientation you may be, is healthy or desirable. Just because a significant, and increasing proportion of the UK population is obese, doesn't equate to obese models being socially acceptable, or even obese people being accepted in society.
I've seen cases where Kate Upton has been described as 'plus sized'. There's a difference between some curves and obesity. Some men do like "bigger" women.
But equating it to acceptance of anorexic models is the wrong thing to do as well. Different health problems completely.
An obese woman is more ostracised in society, than a man of the same weight would be. That's perverse, and needs fixing. An anorexic girl sadly has, and is all to often, been deemed as an attention seeker...despite so much pressure in our society to conform to some sort of unrealistic ideal. An anorexic boy also...and yes, such cases are increasing.
Yes, we shouldn't fat shame, or skinny shame for that matter in society, but that is not to say that being super-obese or super-skinny is ideal.