I don't think this thread is for AIBU really, it's a sensitive subject.
But I think YABU for what it's worth, which you won't want to hear. My DSIS was going through IVF when I got pregnant and she wouldn't have anything to do with me. We now both have children and love each others' kids to bits but that has always jammed a wedge between us.
She is not responsible for how you feel- you need to get help. Billions of other people will have children, so you can't get upset over every one. People have their own lives.
That said, they should understand that this is all pretty fresh for you and you're hurting, so pushing it in your face is probably not the right way to do things.
I'm pregnant again now and my best friend has cut me out of her life because she wanted to get pregnant before me. She'd been trying a year and I fell pregnant on the first month, lost it, and fell pregnant again straight away. But my God, this pregnancy has been worrying- so I have my own problems going on. She already has a DS so I think she should appreciate what she has, what she's had the chance to experience, and stop being bitter over a dream. Many people don't have any children at all and they find it in themselves to be happy for other people.
I'm sorry you're hurting, but I think the same applies to you. The problem is with you, not her, so you need to get help for it and learn not to be hateful towards people who have got children.
You need to find someone to rely on for support and unfortunately that's not your sister as she's not in a position to offer what you need.