grumble, grumble

I was having such a  nice day until I just spoke with my secretary at work.  During the summers, we get to work a 4-day work week, and I have Monday's off.  However, Charlene went to an orthopedic surgeon this morning about her knee, and I wanted to see how she was doing.  We chatted for a bit (she has to have an MRI tomorrow and they think that she has a torn meniscus) and she told me that the one thing that she wanted me to know about now was that we had an upset parent that wanted me to call her first thing in the morning.  The mother is upset because she didn't get a notice about the summer graduation program for her daughter.  When she spoke with the summer school principal, she was informed that I never told them that her daughter was eligible to graduate in August and that I never put her name on the list that was sent.  WRONG!!!!  Fortunately, I make sure to keep notices, lists, and e-mails about important things just in case.  I have the e-mail that I sent, with the list attached, and the girl's name is most definitely on the list.  I don't know if the summer school principal inadvertently deleted the student off the list or if she just screwed up and didn't invite the parent.  Either way, the fault lies with her, but she has pawned it off on me as if it is my fault.  I will be the first person to tel you that I make mistakes, and I will own up for those mistakes.  Hell, I have even taken the fault for counselors when they have made mistakes because they are part of my department, and if they screw up, then some part of the fault can lie with me as well.  If this were my mistake, I would take responsibility.  HOWEVER, it isn't.  My quandary now is whether or not to throw the ball back into her court or not when I talk with the mother tomorrow morning.  I can try to smooth things over without placing blame, but the summer school principal had no problem throwing me under the bus.  Should I give her the same courtesy or should I take the higher road and be more professional?  What do you think flist?