How to punish disobedient best friend?

Excuse me? You're only 'duty' as a friend is to have good times with them and listen to each other. Stop talking about 'disobedient' bullshit, you've got no authority over her.

Yu don't punish friends. ANd inanother post you were compaining about no body eating at yourwedding. I had a feeling you were a troll when yousadi the drink was grape juice-wine-and dr pepper.

Be the better person and don't spread rumors or anything of that sort. Be respectful and caring even if she didn't do what you asked to. You don't get everything you want in life. Go talk to the boy yourself.

You're lucky that an angry parent hasn't approached you... I would never recommend starting a rumor.

Once a rumour starts, it grows in intensity and can't be stopped leading to possibly devastating consequences not just for your friend but for you too. So she didn't do as you asked - or did you command? - so what? That's her choice.
Please do not smack her either as you'll get a reputation as an aggressive individual and I'm sure you don't want that following you around.

How about nothing

Tell all your other friends so they will be on your side and then come up with something together, more minds are better than one