Nothing with high fructose corn syrup, no sweets.
Learn to read the labels. Try to keep fats, saturated fats, sugars down as well as cholesterol.
Dont go crazy with carbs, try to eat whole weat, rye, stuff like that when she does.
Stay away from anything with trans-fat if at all possible. Most fast food restuarants use it to fry the food. Its in most packaged snacks such as peanut butter crackers, cheese its.
She's got to work slow and one thing at a time. So many people who try the diet and exercise thing jump in completely and get over whelmed. Start with no fast food and soda. When shes got that down add in something else. Eventually if she sticks to it she'll be dropping weight and it will be more of a way of life than a change.
Im sure someone may say something different but thats my opinion on where to start.