Who is more important, you or them? If you give in and drink because of the way they have acted then you are making them more important than they deserve to be.
Whether you drink or not is up to you. Nobody is putting a gun to your head and telling you to drink. You will be consciously buying the alcohol, pouring it and drinking it. It is your choice and your choice alone.
I'm not trying to be nasty, I'm speaking from experience. I've blamed everyone and their mother for my drinking but there is one person to blame and that's me.
Rather than drink, take their actions as a challenge. Stand up and say "I can do this without you", because you can.
As I say, please don't think I'm being judgemental or nasty. That really is not my intention. I would just hate for the past 15 days to go to waste or for you to wake up Thursday morning feeling bad about yourself.