Direct answer
Ask what the guest needs avoided and what precautions they request. Do not treat lactose-free as milk-free or vegan as proof of an allergy-controlled path. Verify milk, cream, butter, cheese, yogurt, ghee, whey, casein, caseinates, milk solids, compound foods, and every substitute. Then check the grill, fryer, steam wand, blender, utensils, brush, garnish, ticket, and pickup before accepting.