Hi RD, Snowdrop, garlicbutter and everyone.
Snow, I think it is ok to treat your Mil different from your xmom. You feel differently about them and that in itself justifies what you send or don't send. I know that looks good on paper, but in the operation of it-it is a boundary: you respecting your feelings.
I have two sisters born on the same day, two years apart. I had been trained to always give equally, in dollar terms if not in physical artifacts, no matter what. Now, I don't. My oldest sister is my 'enlightened witness' and Understands; my middle sister is (possibly N) the toxic one.
RubberDuck,
That is an essential mantra! I need that one too. Another one, slightly assiociated, is: "Stop stirring the (stew) pot". I lug that stew pot everywhere! Damn if it isn't time to put it down and plant some petunias in it! 
Good luck on the Mother's Day. Mine is deceased many years and I don't have much exposure to mil (500+ miles away
). I guess folks get an expectation of attention over it...I have spent my life avoiding attention so I hope I don't turn into one of those that feels entitled to pout if I am not "made to be happy".