Children (and you are, IMO, still a child

) shouldn't have to raise their parents. That must stink for you. If I were you, I would try my hardest to find homes for all the animals- as much as I know that pains you- and move out. Anywhere. In a 1 room efficiency if you have to, and live on student loans.
Your #1 job- Bri- is getting an education so that you are not dependent on another person in your life. You are not 'turning your back' on her (frankly, I think she has treated you shabbily for a while), you are making the most of your life. It isn't your responsibility to get her to seek mental or physical help, to put food on your table, or anything else. She should be doing all that for you (provided that she is financially able). I can't imagine stressing, at your age, about food and gas, and whether my parent was getting out of the house that day or not. Good grief.
If she wants to get help, she is an ADULT. She can and will get help. Otherwise, she is going to bring you down with her.

Bookmarks