I can only speak to DLR, not WDW. They do not offer a Canadian Military discount for tickets or rooms, only for US Military and Vets. I try all the time (I'm a vet, hubby is RCN), and I can get discounts at good neighbour hotels, various other places, but not at a Disney Park. Fortunately, there's a Post Exchange nearby - at the local Marine base just south. If there's a base nearby, your friend can order tickets over the phone (ITT services I think it's called) and get the military discounted ticket. They may need their military ID at the gates, however.
I hope that helps a little.