Hi Invisibledaughter,
How about honouring your feelings and doing what feels right this year, for you? Your mother already established last year her feelings about mother's day. Maybe you could take her at her word and just let it go by?
That way, you can honour both your feelings about it and if you have any reaction from her or any feelings about it later you can take time to examine what they might mean, without the pressure of the day itself.
SaB