Letting your friend know that you are there for her is good, however when a woman loses a child through a miscarriage, they sometimes do not see that people are there for them just by saying it. It is the little things that you can do for your friend. Be there to listen and cry with her, send her a card or e-mail, flowers even show that you care and are worried. As they say, actions speak louder than words! I had two miscarriages in between my two children with the first one being devestasting and the one thing I know that I personally resented from friends and family was the following statement. "Don't worry there will be other babies to replace this one." This is the worst thing someone could say to a woman who has just lost a child. One child does not replace another, so how anyone could think that is beyond me. In additon, check with area agencies and see if they have some sort of Bereavement Program for parents who have lost a child, through miscarriage, stillborn, etc... I joined a program like that in my community and it really helped. Also, the best thing your friend can do is journal her thoughts on paper about how she is feeling. However, if she is keeping the feelings all bottled up inside, then she may need to seek professional help.
I hope this helps.
M.