Heartbreaking

I'm at a loss for words after the following conversations with one of my dear friends. And I am one of two people she will likely ever have this conversation with.

Me: Hey, sorry I didn't call you back right away. This weekend was busy, and I wanted to make sure I'd have time to chat for awhile (read: I forgot and meant to call but was busy whenever I thought of it which wasn't often enough)
Her: That's fine.
Me: So how're you doing? Still loving the new house?
Her: I've been better.
Me: That sounds familiar. Did you at least get the gaslines hooked up so you can dry clothes?
Her: (no real answer)
Me: So what's going on?
Her: I've been better.
Me: Anything you want to talk about?
Her: Maybe later. What does your week look like?
Me: Well, today's super busy with stuff except for my break now, tomorrow I'm working from home and ditto with Thursday. Hey, Friday I'll be in the city for a girls' night. Maybe I can catch up with you before we head to dinner. And I'm assuming we'll see you on Saturday, right? Why do you ask?
Her: Oh, I just wanted to see what you were up to.
Me: Are you ok?
Her: I've been better. I have some bad news.
Me: Ok.
loooooooooong silence
Her: choking and crying some (me thinking that her mom who's a breast cancer survivor got some bad news or something along those lines but staying silent to give her time)
Her: I'm pregnant. But it's not viable.
Me: OH! I'm so sorry. I can't imagine how devastated you are right now.

The conversation continued for a little while after that, and we were able to talk about it some. But suffice it to say my dear friend who is already convinced she's too old to be a mom just found out that they have to take her baby. You have no idea how much she and her husband want children. How desperately they have been trying since getting married. How wonderful they are with my own children. She will be able to try again, but ... I'm at a loss now.

How do you support a friend when they suffer such an intensely personal loss. My friends aren't even telling their parents. And yet I know how hurt they are, especially her. And yes, I feel like a heel for not having called her back on Friday night when she called me.