Do I want Her back here?

No I won't, with that behavior of her's is no different of abusing. She choose the responsibly to take good care and be like how a good mother should be towards her children. Whether step- or flesh and blood, it is the same. Worst she takes drugs, drinks etc. So what if she done so much for you and younger sister. She wants you and your siblings out of her , her children and your father. Then where would you go? She will just torture you and your sister till you all will really run away then she is happy. Unless she change that attitude and those bad habits :taking drugs, smoking, drinking etc. (remember not to take any chances) completely and not just for pretend. You and your sister should also keep in good relationship with your father. In case, that step mom of yours is trying to steal him away from both of you.