I'm confused. You made a commitment to your sister to go on a bender? (I ask because you said you don't want to choose between family and T, so I'm assuming T would be against this and therefore your sister is encouraging it?)

I'm not so sure you are unwilling to help yourself or you wouldn't be asking these questions in the first place, right? T needs to know this is going on in order to help you past this. Can you find something healthier to do that won't leave you with the regrets that you seem to already be feeling?