How good is she in taking disappointments? Just buy it and try to avoid the whole "when to open" debate. When she's not around, open it and afterwards apologize with a goofy grin ("sorry, couldn't help myself
). She might pout a bit, but how can anyone really stay mad long when their only argument is "but you will appreciate it more if you wait" when you already
have it? Most likely she'll secretly enjoy using the new TV already, though she might not admit it (maybe not even to herself).
Then again, the fact that she wants to wait for Christmas makes me think that she puts
a lot of value in Christmas and won't respond in a logical manner. In that case, I'm glad I'm not you