My first reaction is that you should not pay any of her bills at all. Even though she has been sober for two months, I still see it as enabling. Who is to say that once your family has cleaned up her financial mess, she won't think "wow, that was easy", and start drinking again?
That said, my brother is an addict who is majorly enabled by my mother. And I definitely can not say I've never contributed to that madness. It is so painful to see someone you love struggle; you just want to make them better. But maybe enabling them is more about assuaging our own uncomfortability with their struggle than actually helping them?
I think you really need to get clear about what the healthiest thing for your sister is, and then go with that. I feel badly for you because these family things can be a real mess.
(If you don't help pay, the burden is falling on everyone else, yet they are choosing to do it).
I'm sure you will get some great advice on SR. I am a newbie but wanted to try to support you.
DoS