Mother In Law help!

October Momma • 22 year old happily married mother of boy girl twins, Emma and Alden, born 10/11/17😊
So I will try and make this short. My husband and I have been together nearly 4 years now and married for almost 3 of those years. We are 15 weeks 2 days with twins, these are our first kids. I'm 22 and he is 24 and we used a fertility specialist to conceive because of my issues. His step mother has said maybe 10 words to me since the day I met her nearly 4 years ago. She told his entire family horrible things about me that were completely untrue, everyone told me everything she said the night of my reception. Due to the tension in our families and our personal issues with weddings, my husband and I chose to elope. She has been mad at us for this for nearly 3 years now. When we go over she hides inside or in another room and won't talk to us, at holidays she hugs everyone but me so I know I'm not welcome, when we tried to sit down and work things out she made other last minute plans to avoid it, when we talk to her she pretends she can't hear us, when we talk to others she will talk over us and pretend we aren't speaking, when we announced our pregnancy via text like his father told us to she didn't respond and claimed she didn't get it even though she replied to the same thread days later about something else, etc. When my husband lived at home she would give him chore lists the minute he went to leave the house to meet with me to try and keep him from going. He would refuse because she knew about our plans all week and he was 21 and wasn't going to cancel. If he didn't do everything she wanted she would call him names and take away his phone and go through all of his texts. For 2 years we have worked hard to be nice and civil no matter how horrible she is. We have ignored all the harsh things she tells others about us and smiled and turned the other cheek. We are now having babies and feel like we can no longer do that. We don't want our kids thinking that's appropriate behavior and we don't want them thinking they can treat us the way she does. When we tried to talk to my father in law and let him know that the behavior wasn't ok and she wouldn't be allowed at the hospital during the birth because she has made the relationship so strained we were told we were the bad guys. We have tried for 2 years of our marriage and 3 years of our relationship to make this work and make things better but she isn't interested in that. We were told we have to let her do and say whatever she wants because if we don't the entire family will have to cut us off. Am I the only one who thinks it's insane that we either have to roll over and be treated like crap in front of our children or be disowned by his family? Why should she just be allowed to say and do whatever she pleases and no one is allowed to say boo?