First off, I would be feeling the SAME way you are feeling. Did she even apologize or offer you more time next time or anything? I would TOTALLY email and tell her how you feel. I would tell her what you expect the next time it happens (hopefully it WON'T).
Maybe she doesn't realize how much it affected you.
Now that I think about it, I would probably be late the next time....but that would just be "my" revenge and would just rip off more time.
((((Jbug))))