I’m sorry to read what you are both going through at such a young age, this would be so difficult for an adult to deal with and it sounds like you are mature and want better for you and your sister so that’s already an amazing positive step.
Neither of you have to be alone in this. You should definitely seek out support for you and your sister from a drugs and alcohol service. There will be supportive adults there who can point you in the right direction and give you some practical advice.
It’s hard to deal with at the moment but in years to come this will make you the best parent because of the mistakes they have made and are making.
All the best