My heart is breaking...

My sister is the most wonderful Auntie in the whole wide world! She is a special ed teacher and is just absolutely amazing with children. She loves mine like her own and I'm forever grateful for her in my children's lives! Why is my heart breaking? She has been ttc for 8+ years with no luck! Nothing wrong with her, she's been checked, just nothing happening for her. And now, I have to figure out how to tell her I'm pregnant with #3. I'm beyond excited for this baby. But why can't it be her?? How do I tell her, it's eating at me and it's so depressing for me because she deserves a baby so much more than me and I can't help her. How do I do this? How do I break my amazingly wonderful sister's heart, while mine is bursting with joy for this new addition😔 I'm so conflicted