Me and my sister a few years back was 2 weeks apart, I lost mine and my niece was fine. It was hard on me that I lost mine and seeing her grow yes but I would never want her or anyone to deal with a m/c. My niece will be 5 July 3rd and I will be having my lil boy on Monday. Just let her know you care but don't over do it. Time heals everything. And let her talk about it when she feels up to it. It might be hard on her for a while after the baby is born or she might be fine. I couldn't hold my niece with out crying thinking about the baby I had lost. But it did get better. Just show her you love her and try to include her in things
I understand how you feel. My best friend and I got pregnant three weeks apart but she had an abortion and I kept my baby. I always feel guilty talking about my baby so I just never mention it until she starts a conversation about it because I don't always know where her mind is (some days she regrets it, some days she doesn't) I know it's not entirely the same situation as yours, but the feelings are similar.
I understand. It's not your fault that this happened. But it's still hard. Let her take the lead. When you talk to her take cues from her. Hope all continues well for you.