I'm going to agree with everyone here..the best thing you can do is be there for her.
This is such a sad and terrible thing to happen; it's going to be a tough road for her and the baby's father (don't forget about him, if he's still in the picture--dads grieve, too).
Let her take the lead--if she wants to talk, then by all means talk. If not, then don't try to force her.
A shoulder, a comforting word, someone to cry with all help. Sometimes, if you don't know the right thing to say, then don't say anything. She'll know you care by your being there.