HDDR has been one of my BEST meals for the last two years and I'm allergic to the same things plus many more foods! Be sure to contact special diets and fill out the form. You can always request that a chef contact you (I often do but my list of avoidances is over 25 so I like to discuss the plan with the chefs if I'm going to keep the ADR), but I have no doubt that they will be able to accommodate her even if the chef simply talks to you at the beginning of the meal. Be sure your server knows she needs to talk to a chef if you don't get in contact with them ahead of time. They always know I'm coming and sit us right by the kitchen which is also very close to the stage!
They always make me grilled chicken, ribs, corn, sautéed veggies, mashed potatoes with rice milk, and roasted cinnamon apples as dessert.
I hope she has a great meal!