Oh, I am in tears! Your story sounds so similar to mine!
I lost my baby boy Noah in Feb 2006. My DH and I had been trying for him for 17 months. When I was 12 weeks pregnant with him, my sister announced that she and her DH were expecting their 3rd baby too and she was 6 weeks pregnant at the time. They didn't try for him, they were just lucky
I was so excited to be sharing my pregnancy with my sister! But, when I lost Noah, all of a sudden I went through a million different feelings about my sister still being pregnant. It was a really sad, dark and scary time for me.
My sister bought me a beautiful wood carving of a mum and a baby that form a heart shape. That meant the world to me. She acknowledged my baby. She understood my pain. She kept her distance when I needed her to, and got close to me when she knew I needed that. I know the remainder of her pregnany would have been difficult too. Because she knew she was having a boy, she also had the fear of something going wrong too.
My heart is seriously breaking for your sister. What she is doing is out of grief. I hope she gets the help she needs before she loses her marriage also. I would tell your parents. If it were me, I would want them to know I'm not coping. I am sure they would want to know also. I'm not sure what type of relationship your sister has with your parents, but I know I needed my mum so much... Through all my grief, I forgot she was grieving too... she lost a grandson, and she talks about Noah to me all the time.
I am sorry if what I have written makes no sense. Your story has really moved me
Please feel free to contact me on my email address in my profile if you ever need to talk.