When she says, "I don't need anything for Christmas..."
What she means...
Buy something that makes you think of her. Her favorite candy. Her favorite beverage. Her favorite method of relaxing. A letter praising her efforts that continuously go unnoticed. You thinking of her and recognizing her is the best gift.
Because you know she just spent the last 30 days thinking about everybody else except herself, like she does every day.
It is your turn to think of her... Make her feel cherished.