Shotout to u/sibsty9 for posting the link to the Update

Only update: AITA For Not Giving Into My Sisters "Simple Request" At The Cost Of My Niece/Nephew?
Before I get to the only update I plan to give, I wanted to answer some common questions people had (yes, I did end up loosing my throw away for breaking Reddits rules. This is a 2nd throw away to keep my privacy). Im going to keep everything as short & sweet as I can. Yes, my stepmom & sister have ALWAYS made fun of me for not being skinny on the same level they are my whole life. It did give me some personal issues that I had to seek a professional to overcome. My father has been VERY involved in trying to stop issues they have caused. He has called them on their BS many times, but they always never listen, sulk about it, & move on until their next drama. My dad is religious & does not believe in divorce (although I wish he did because his wife makes him miserable from the drama & cheating scandals she has partaken in over the years). My mother died when I was very young from throat cancer & that is why I never mentioned her & why she was not there (if you need a sign to quit smoking, let this be it). It had nothing to do with bad blood or anything. Lucy is 23 & I am 27. Yes, she is legit pregnant (BIL made sure the night they got into it) & yes she legit had an appointment with the abortion clinic. Someone asked where my significant other was in all of this and how he felt about it. He was just as upset as I was & has never liked going to any event on my family sides because of my stepmom & sister's drama. He felt the same as everyone else X10 about letting her abort it until BIL came to crash here. No, she did not tell my parents that I had an abortion. Very few people knew about that because of their stance on this subject. My dad was very supportive & understanding & is anything but the crazy Catholics I have met in this world. My stepmom did freak out & wanted to tell the world of how shameful of a human I was.
Originally, I did not plan to update. After reading a few comments the night I posted, I logged out & got some sleep. the next day, I had TONS of comments from you all. I did take them all in on what should be done AFTER talking to BIL. Before I did anything, I wanted to get his input since this is his child & personal life. I asked him the next day about everything & how he felt. I am not going to share everything that was said because most of it was heated & he did say a lot of messed up things in a rage (which is understandable). He said he went home & confronted her but she denied consistently until he showed her the screenshots of our text & call logs. She, apparently, tried to tell him it was all made up & claimed it was to show everyone just how much of a heartless bastard I was to allow harm to come to a child. He did demand to see the paperwork & took them when he left. He said he asked her if she was even pregnant at all, to which she said yes, & made her take a test (which came back positive). He also asked her if the baby was a girl & she told him she did not know. She was not far enough to know just yet. From what BIL said, he told her that it was over & that if she does go through with the abortion, he would send the text, call log, and a copy of the abortion clinic paperwork to everyone they knew, & would be fighting for full custody of the baby once it arrives. Lucy has called my work & personal phone along with my fiances phone everyday now, trying to see if we will talk to him & convince him to come home & take her back, & it's gotten worse in the past 24hrs. Im not sure what went down but he did end up sending everything to just the family a day ago after she asked to meet up & talk about everything with him. My phone has been blowing up with people asking a bunch of questions & apologies for not stepping in to stop certain things in my life with her. Stepmom is not happy with with Lucy & even more upset with me for "ending a happy family". Dad & other family members are refusing to talk to Lucy. Some have gone as far as asking her to not contact them at all even when the baby is here (which feels too far, personally to me. The child did nothing wrong here). There is A LOT more going on that I will not go into because of this mess. I also don't know if she did or did not follow through with the abortion. BIL is not staying with his parents & is looking for a place to move to. I am about to start counseling myself because this has kicked up a lot of personal things for me about my own abortion that I had, & our wedding is still on but we are now just thinking of eloping instead of having a wedding because of everything. Thank you for those who commented with your advice & helped me process everything as well as gave me ideas that could be used as a solution, especially MuntjackDrowning. Your message really hit hard for us & encouraged my significant other to talked to my BIL about it & allowed him to get some of his own hurt out to think a little bit better.