Hello Lady, I think that you did the right thing. Because if that girl was drinking while babysitting. And something horrible happened due to the use of drugs/alcohol, you would be so upset that you didn't do something. There's nothing wrong with looking out for the kids you coach and teach. Especially that she is only 14 years of age.
She might not like you right now, for calling her mom. But later on when she grows up, she will realize what a caring, responsible human being you are.