One thing that comes to mind to help disarm the attitude is to use Bauman to it's fullest. And for that matter, research in general. For example, showing them the E4H model and saying "this is how the school I am attending reccomends you spread your nutrition and eating and we can talk about some ways I have done it, and then we can talk about some ways I have read other people have done it, and then we can talk about your day and figure out what we might be able to do with it".
The trick is explaining it and/or presenting it in a manner which is not saying "I know more than you and so do these people", but rather "hey, here are some things to think about". I think that comes across in your conversation, but also in the plan or notes you leave them with. I think people like the conversational route where you are not trying to be the fear factor, but really just trying to be genuine and educated about your response.
I think starting the conversation with a thank you is always helpful too. Especially here because while she may not have agreed with her husband's decision, she is still letting you in the house and giving you an hour or two to chat. That is pretty valuable in itself.
Lastly, I think cooking and eating together is always a good casual, conversation iniator. Maybe you can set some time up that day to cook something for a bit of hands on fun.
Hope these help.