I saw Dr Mosley's TV shows before the specific diet one - I think he has type 2 diabetes himself as well.If she is intelligent and follows a diabetic diet, Dr Michael Mosley does a brilliant one she can hopefully avoid going onto insulin tablets but then that would probably be too easy. Especially if both her parents were diabetic.
I've seen debate on this board (and another site the Gossip Bakery about an anaesthetist 'influencer' Dr Kristina Braly in the US who made videos crying about having gestational diabetes amongst other upsets and problems she was having) saying that having gestational diabetes doesn't necessarily make you at risk of it later on and also that gestational diabetes is just an unfortunate insulin problem because of hormones in pregnancy so factors like weight and diet might not necessarily come into it.