Google low glycemic diet. This is best for everyone but can actually prevent or control gestational or type 2 without medication. (Jenny Craig and Nutrisystems are now using it for their weight loss programs)
Generally speaking meats and cheeses are low glycemic. Most proteins are, however legumes are mostly medium glycemic. Most nuts are low glycemic. Green veggies like broccoli or cauliflower are good. Carrots are a no-no. Fruit platters with higer fiber are best but most fruits are okay. Pineapple is a no-no.....as you can see there is a general rule of thumb but the glycemic index does not have a hard and fast gage.
No bread or crackers unless they are spelt or sprout breads....Mayonnaise without sugar is okay (Dukes is the only one I know that doesn't add sugar) but store bought dressings are usually very high glycemic and loaded with high fructose corn syrup that is a killer!
Bacon, eggs, cheeses, veggies..you could do an omelet buffet too!
If you decide to do a low glycemic menu your friend will probably think you really went all out for her. There are some really cool things you can do with different types of fruits and veggies as well as funky kinds of breads!
Hope this helps!
M.