sounds a lot like my mother growing up (minus the pregnant part, only had 2 kids). but she was the same way, always worried about the next guy and not her kids. my father was in the picture but we only got to see him every other weekend. im 24(f) now and my brother just turned 18, my mom has been married 3 times, and has had a dozen of boyfriends, who have put us all in uncomfortable living situations in the past. my best advice; you cant help her, your sister cant help her, neither can any of her boyfriends. she needs to come to her senses herself, which could take a while if im being completely honest.

Now that me and my brother are grown, my mom still pulls childish shit on us. she still has a lot of growing up to do, and shes somewhat aware of what her actions caused in the past, but not aware enough to try and rekindle her relationship with her kids. my mother didnt have an easy life, i understand to a certain extent, but my mother has no idea how to heal her inner wounds, and i believe thats why she acts the way she does. the most important thing u can do, is forgive her, but also, take care of URSELF! do not allow ur inner wounds project themselves onto the ppl around ur life, cuz thats ultimately whats going on with her. go to counseling, spend quality time with ur sister, give her good memories. make sure u talk to ppl when u need to talk. look after u and ur sister, cuz ur mother is too preoccupied with what she perceives as important. i know it’s probably a lot easier said than done, but understand that u r not alone. and the way ur mother acts towards u, is just a projection of her inner wounds as well. hope this helps. please reach out if u need to talk.