I had a lot of friends that fell pregnant right after I had my stillborn (like 12 people!) and I know that, for me anyway, it wasn't a big deal. But I didn't have any problem getting pregnant and Macey's death wasn't do to any health problems on my part. I felt more like every time I saw anyone that they expected me to be bawling or to be happy and pregnant again, like I had to choose one or the other. If your friend has had infertility problems and then had a miscarriage I would think that would be harder and can understand how you would want to be more attentive to her feelings. Maybe just tell her when its just the two of you over coffee or lunch, etc., and then explain that you weren't sure how to tell her but try not to act like you feel bad for her. I remember that was the crappiest feeling ever; to know that on top of being depressed, that everyone felt bad for you or pitied you.
**After reading the PP I wanted to add that when the first one of my friend's baby was born I know I felt a lot of resentment towards their baby but was conflicted because I was also happy for them and the baby was so cute. It took me a couple of weeks of seeing the baby once a week at softball before I felt like I was ready to hold the baby and not feel any resentment. I felt like it was disrespectful to hold the baby and have secret resentment and jealousy. I don't know if any of this helps. Sorry. I think, though, that it will just be better for her to rip the band aid of, so to speak, and then she can process it and heal however she needs to. You never know, she might not even bat an eyelash.
AND CONGRATS TO YOU!!!!