As long as she stays within the room capacity she can add others to her reservation, but they will need to book the same tickets that she has. Final payment is due 30 days before arrival date and once within the 30 day to arrival timeframe she can add someone, but immediate payment will be required. There is a change fee within 30 days, but usually it is waived if the total cost increases. For a paid dining plan you can add someone up to 3 days before arrival and still get the dining plan for them, but I don't know if the rules/deadlines are different for a FD package. You can check the terms and conditions of her package for the info.