This is pretty much what I was going to say but I want to add that unless your T is a nutritionist she really shouldn't be managing your diet. The feelings behind why you eat and eating behaviors are what she should be helping with.

Changing your diet is a great step to becoming healthy but with that much to lose you should have the support of someone who will understand your body's dietary needs and guide in going vegan in a healthy way that will support your weight loss.

After I had my d I had 70 lbs to lose so I know what it feels like to struggle with this issue :. Just remember it takes time to make changes and like everyone has already said it will stick better if it is a gradual process instead of making and trying to stick with abrupt changes. Goog luck!