Sounds like she's looking for something to be mad about, and she's grasping at a straw. You very nicely offered to stay home with her daughter on Thursday. The daughter shouldn't require the both of you there on Tuesday. That would be making an overly big deal of this procedure. It is an ordeal, but this isn't brain surgery.

You could bring her dauhter a small gift on Tuesday eve - like, maybe, a small stuffed animal.