And now for something completely different yet the same

my ex-husband and my daughter got student loans now totaling $80,000 for BS degree. She is living with my new husband and me after starting her 1st "real" job. I got an email from her dad with all of the expenses he has since she has now graduated. I agreed to pay half of one student loan taken out but after a couple of payments, couldn't afford it. He had never given details of the loans and never discussed it with me before getting them. Some are in his name but $40,000+ are in daughters name. He is horrible at communicating and always avoided it until desperate and then it's rude. He told our daughter that since I started getting some retirement money from him and the amount, that I should be able to pay for these loans. He's hounding her to confront me and wants to know what I'll pay. I have no problem telling him to kiss off, but it's hard to tell my daughter that. I am intimidated by her (sometimes) and her living here makes it harder. Some may say that living here, rent free, is a healthy contribution but I'm really struggling with the possibility of this ruining my relationship with her. Having said that, my husband feels she is disrespectful to me and doesn't deserve what is being asked through her. This is torture. I plan to tell her that she and her dad got into this mess, they need to fix it. My best advise to their extortion attempts is to default on the loans. She says it'll ruin her relationship with her dad. Looking for objective advice and opinions, please.