My concern is mom's seemly bizarre behavior going from overly concerned mom who is in the ER to a self admitted "crazy mom" who had level enough head AFTER leaving he ER to do a little shopping????
I would be having a face to face discussion with this mom about her accusing you of something.... I mean that is pretty serious and for her to put you in such a stressful situation by saying that it happened on your watch without even acknowledging that her children can be out of control and overly rough a majority of the time!!!!!
THAT would NOT fly here.....
I totally understand that things can and do happen at daycare but the way this whole thing went down warrants a sit down conference in my opinion.
She needs to be told that you take your business VERY seriously and professionally and that her lackadaisical attitude about the way her children behave is sad and not something you will continue working with if she is going to willy-nilly accuse you of something every time the kids get a red mark.