Husband's wife came back

Me and my husband are common law married. He has a 17 year old son and a 13 year old daughter. His wife walked out on him 11 years ago and left her kids behind to go back to England. We are currently pregnant with our 3rd. I consider his kids my kids and they call me mom. He divorced his wife 8 years ago. Well he thought they were divorced... She was at our door step 3 week ago. He hasn't seen this women in 11 years. Their son answered and she hugged him and he literally said. "Who are you?" She saw my husband and ran and kissed him. He was in shock but then pulled away. She was saying she knows it's been a long time but she made a mistake leaving and all that. Then she saw me. She asked who I was and I said his wife. Then she said she's his wife. He said they divorced 8 years ago and she said they didn't because she actually never sent the papers were they were supposed to go. This was a shock to all of us. She then called me a homewrecker? My husband made it clear he doesn't want to get back with her. He got new papers drawn buts she's refusing to sign saying she wants her family back. By family she means my husband because over these 3 weeks she's made no effort to actually be with her KIDS. Not like they want anything to do with her to begin with. She is now saying if they divorce she will take everything and leave all 4 almost 5 of us homeless.... And is begging my husband to give her another chance. He's getting a loyal. What kind of mother threatens to leave her own kids homeless. My daughter is freaking out and had anxiety and I'm telling her I'm not gonna let that happen. She's saying if my husband spends the day with her and decides he still wants a divorce she will give it to him but my husband is saying absolutely not.... I just want this to go away... I'm 5 weeks away from giving birth. She's stressing me and my kids out ..

Edit: My husband married really young so he didn't know you were supposed to get papers stating it was finalized. He's getting a loyal and ig legally.... She is the real wife..

Oh and a psycho thing she told me when she came back to talk to him because he wanted to discuss the divorce. She told me I had a nice ring but she's legally his wife and if something was to happen to him before he can force a divorce she will get all the assets and leave me and my baby to rot... She said her children can choose to rot with me if they want...