"... whether or not I should tell her parents tomorrow when i take her home."
Please, OP, tell me that you were joking when you said that!
Of course you have to tell her parents! Because they are her parents and they need to know what their child has been up to. Chances are that either she/the other children have consumed spirits which you know nothing about (not your fault, teenagers are sneaky buggers about things like alcohol) or that this particular child is allergic to alcohol. It does happen, it is a possibility (my father is allergic to it, so...). But even if she's not, then they still need to know.
I'm pretty liberal when it comes to teenagers and alcohol - but only my own and only under the supervision of responsible/sensible adults. Which means that if I were the parent of your daughter's friend? She'd be banned from spending any time with your child and/or at your house. Until she turned 18 and was no longer legally my responsibility, I'm afraid. If your daughter's friends parents are more "meh" about their child's safety, then you/your daughter want to consider yourself fortunate. You, in particular, if they don't report you to the police for supplying alcohol to a minor child. I would, if I were them.
She might have choked on her own vomit whilst you were out, OP. She might have seriously injured herself through drunken stupidity whilst you weren't there to supervise. That's not a risk you take with your own child... never mind someone else's!
And if you teach parenting classes - then perhaps you need to reconsider your career choice. Because, frankly, I don't think you need to be dispensing wisdom to other people when you screw up like this with someone else's child.
(Yes, liberal use of the word "child", I'm afraid, because that's what your daughter and her friends are. Children. They might have a "teen" in their age, but they're legally classed as children for at least another three or four years.)