Wow, with all the suggestions no one mentioned broiling the steak. I sounds like she is a simple meat and potatoes girl. For your first dinner, keep it simple. You don't need to over work this.
I would find either a couple of nice rib eyes, or a flat iron steaks. A jar of montreal steak seasoning from the spice isle in the store.
Sprinkle the meat lightly on both sides. Get the broiler hot, pop the steaks under the broiler for about 3 minutes each side.. check to see how done they are. If it's an electric oven, the meat needs to be pretty close to the heating element. Maybe not the top rack position, but well above half way. Gas stove, the broiler is the broiler....
For the potatoes, I would think about offering up a course salted baked potato(dampen the potato, roll in course sea salt) or give her the option of a baked sweet potato with brown sugar and butter..
Make a nice salad, various dressings, garlic bread and find a good desert.