Stuck between a rock and a hard place..

My little sister(she’s not so little... 22) has struggled with addiction since she was about 14(strong stuff. Meth, heroin etc.) she’s not my blood sister her dad married my mom and then they divorced but she’s my sister and we kept in touch. She got pregnant several times, had abortions and miscarriages. She got pregnant just before her 20th birthday and this one stuck. Her son is now almost 2 and she is a good mom. Except.. she used drugs throughout the beginning-middle of her pregnancy. She claims she was clean by 6 months but I don’t believe that and she smoked cigarettes the whole time she says only 2018 doctors care that she smokes that it does no harm. Whatever. Better cigarettes than meth. He’s a healthy, happy toddler. That’s most important. She called me about a month ago and said she wanted to come home meaning she needed a place to stay and she knows I’ll always welcome her into my home. She was using again and was clearly high when she called me(FaceTime) while her son was climbing on her, they were laying down.. she’s always around her son and that concerns me too because she obviously has to do drugs to get high and I’m hoping she’s smart enough not to do them in front of her son at least. Anyway I called our dad and told him and he basically said he knew but she won’t admit she needs help or whatever and they’re 650 miles away from me. I tried to get her here but she refused(not abnormal.) she swears she’s clean again, now. And then, last night she sent me a picture of four positive pregnancy tests. She is single, no job, she moved back in with her mother which is who got her hooked on drugs to begin with. Says she is still clean and she’s excited but I’ve never known her to hold a job down for more than two weeks. The whole video chat she was smoking cigarettes which just thoroughly pisses me off as well. I don’t know what to do or say I want to distance myself but what if those babies need me. I hate her for doing this. I love her because she’s my sister and she needs to know she’s supported. But how selfish can you be. I offered to adopt this baby because she’s already struggling with her son obviously with no job. I send her money to put diapers on his butt as it is. I have a son of my own(after YEARS of infertility and almost losing him several times! Which also upsets me I take care of us I work hard I never touch drugs or alcohol or anything and I can’t get pregnant but she does these horrible things and she gets pregnant accidentally!) sorry this is a stupid long rant and rave I just needed to vent. Most people will say call DHR I’m sure but it’s not that easy. This is my sister and she is a good mom... she just has issues and she isn’t helping herself and she won’t let me help her...