She wouldn’t cope on the GD diet. It isn’t just things like cake and chocolate, but carbs which are in things like carrots and peppers. It’s basically a high protein high fat diet with some carbs (the protein and fat will slow down the release of the carbs meaning sugar levels won’t rise so quickly, which the body is struggling with and unable to manage any longer due to the hormones in pregnancy). Her diet is absolutely appalling and while her diet won’t necessarily mean GD, her weight is going to be a huge factor.
She can joke all she likes but GD is serious and comes with additional risk factors to both her and baby, during pregnancy and afterwards.