I kinda hafta go along with the majority on this one...........sounds to me that you couldn't have done it "right" no matter what you chose.  Maybe it's just a bad day, maybe it's hormones (my personal guess), maybe there're deeper underlying issues and this is just the manifestation of that.  In any event, I doubt you're going to be able to make it better at this point.  Serve your penance till she's in better frame of mind.  Do Mother's Day differently next year.  If you're feeling lucky, you could bring it up at a (way) later date when she's in a good mood, tell her how sorry you were to disappoint her, and see if she's able to tell you what was in her mind at the time.