My hubby is not into this way of eating. But here are some things I've done with success:
** Instead of ice cream, I buy or make-ahead my own sorbet (frozen, pureed fruit) and keep it on hand. When they want to indulge, I can too. Or, I make myself a smoothie, using fruit and/or greens/veggies of my choice. If you use some frozen fruits it will be nice and thick and you can eat it with a spoon. It's totally satisfying to me and food-plan approved since I choose the ingredients!
** If you share or make meals together, think of meat/cheese as a condiment. You know how you can make taco salad, and the meat/dairy items go on top? Well, do the same thing with your baked potato dishes, rice meals, etc. Have all meat served on the side (even stir fries). Cook all the meat separately. That way you can share all the starch/veggies, and their meat can just be added as a topping/condiment (ditto their cheese/dairy). It's a slight change, almost never noticeable in taste to many people -- just noticed in serving style!! But we know the differences! And that way, everyone is happy!
** Have someone else be in charge of cooking the meat portion.
** Try making one roast/crockpot/grilling/whatever of meat one day a week, then make it last all week ...... or make a double amount, freeze half, and use a prior week's "half" from the freezer if they want more variety. If you make the meat plain (roasted, grilled, etc), you can adapt the meals for the week with BBQ sauce, gravy, seasoning, etc.
** Think of meals as some of your favorite "buffets" or add-your-own-toppings meals. Like taco bars, salad bars, indian restaurants, etc. Not only is the add-your-own factor a helpful idea (where everyone can add/ignore ingredients they want/don't), but thinking of that fun-factor might help you present it to your friend, too. Atmosphere/mood can make such a difference!
** Sauces and things may be different or substituted, but use veggie broths or stocks in place of a lot of other liquids in recipes.... or pureed fruits instead of oils in baking recipes. It's even fun to experiment. Pureed veggies can make some great sauces, too. Pureed broccoli/veggie broth makes a great base. So does summer squash and tarragon! Ooooooh -- and using fresh herbs when you can! Try making your own version of a basil pesto sauce.
** Soup and sandwich -- and they can have the meat in the sandwich. Make it a veggie soup!