Honestly it's your choice to snitch,speak to a lawyer 1st before you make any decisions.It's just a misdemeanor weed charge,you can't just ignore it but like the op said it isn't the end of the world.
Your not facing a murder or some drug trafficking charge,it's funny your so nervous to save your ass but wasn't nervous enough not to smoke when it can cause you legal problems. Morally I feel it's horrible that you want to snitch when you broke the law yourself and you consider the person a friend.You need to just hire a lawyer and follow there advice.
Honesty it's gonna seem like hell at 1st (it's gonna be,lol) but your parents are gonna forgive you after awhile if you stay out of trouble.I hated telling my mom,I was older then you .She was very anti drug.

