I agree with eat a large meal befor eyou go. Actual hunger can often cause people to give in to temtpation when there is nothing else around.

Talk to y our friend. Explain to her about low carb, that you can't have sugar or refined flour. Maybe point to various low carb recipes online she can look through. She may see it as a challange to her cooking skills and create some new amazing low carb treats you can share the recipe too. Tell her there is big bucks in writing low carb cook books and selling products