Have a quiet word with your best friend, explain the situation and ask her to lend you a bit of money for the evening, as you have said you won't be drinking..................do not fall into the trap of asking him for money. Just get dressed and go.........If he realises that he has behaved badly and offers you money, it's up to you to decide whether to take it, or not.
It may do him good to realise that you still have retained your independence, and it may do you some good, too.
The coming months will see your confidence take a knock, don't let it start too early !!