I don't know if this will help, but with myself being a recurrent miscarrier, I have found some pregnancies more difficult to deal with than others. No real rhyme or reason to it. Some women I had been close to, I found their pregnancies ok to hear about, not easy, but I enjoyed seeing their pleasure at being pregnant, other women I avoided being near. Some women I barely knew when I saw they were pregnant, I could not cope with talking with them and definitely did not want to hear any pregnancy gripes or even the happiness of their cute arrival.
I think you can only take your friends lead, she seems to be interested in how you are doing, and will be hoping that you get the precious bundle of joy that has eluded her so far. Continue to be sensitive to how she feels, such as telling her you have had a scan and have pictures and ask if she would like to see them. If she says yes then go and get them (don't have them in your hands when you ask), if she says no, then just acknowledge that you understand that it might bring back painful thoughts to her, and just say that if she changes her mind she can ask you.
As for talking to her about your fears of miscarriage, I think you can be honest with her, but don't over dramatise it. Just say that you are aware that sometimes things don't go as planned and that whilst you are excited by this pregnancy, you are looking forward to getting further along to a time when the risks of miscarriage are less. Acknowledge that you are aware of her miscarriages and are frightened of going thought the sort of pain that she has experienced so many times. If she is still ttc, maybe ask how she copes in early pregnancy with the fear of m/c. Asking her acknowledges her experience. But if she has stopped ttc, then maybe avoid this topic.
To be honest if she is coping and wanting to try and enjoy this pregnancy with you, she will probrably be ok with hearing about how things are, but just try to balance this with "normal" conversation too, so that it is not all about the baby and your pregnancy.
I hope this helps.