As a former working mother, I agree with the suggestions that have been given you. Actually, even as a working grandmother, I have to be organized and plan. My grandchildren live out of state, and to ensure that I can take the needed time off to go to their birthdays, I get my leave on the calendar.

I also think that you should start documenting her requests, comments, the accommodations that you do give her, the times that coworkers take up her slack, and any other issues with her work that you have. You may need the documentation in the future.

This woman is being completely unreasonable. This is her own child's birthday she is talking about. She likely knew she wanted to day off far in advance. It was her responsibility to put in her request earlier.

Her other alternative would have been to not ask for the day off but just call in sick. One day off doesn't usually warrant a doctor's confirmation, at least not at any of the places I've worked. Now, I am not saying I advocate this alternative, but simply stating she could have done this. I think she is kind of SOL on doing this now, though, because it would be pretty obvious she is lying and making an end-run around office vacation policies.