Homeless,

It is my opinion that you haven't given us enough information about the situation. On the one hand, you say the two of you discussed your feelings about Christmas extensively, but did you also: 1) discuss her feelings about Christmas extensively, and; 2) come to a mutual agreement as to how the two of you would celebrate/not celebrate this year specifically?

If you simply told her you hate Christmas, and don't celebrate it, with no further understanding of how the two of you would get through the holiday season together, then you were being manipulative.

On the other hand, if you did listen to her feelings about Christmas (which are obviously pretty pro-Christmas from your description of her gift giving to you), and the two of you still agreed NOT to exchange gifts, then she is being manipulative.

If you have done none of the above, I'm with the recommendations of people above, which is to accept graciously--and reciprocate in kind. Not necessarily with consumer goods--as Spaw pointed out, maybe doing something really special or meaningful for her will make you feel you haven't compromised your values for hers, yet will still make you feel as though you have been loving and giving in return.