Another who agrees on a non-face to face option. I would always prefer a text over phone call and definitely over face to face - and do please tell her in person and not wait for her to see a Facebook status with a scan photo - those are also awful for someone struggling with fertility issues.
Remember that you are allowed to be excited about your pregnancy but also remember that she's not going to react with excitement, the first thing she will undoubtedly feel is pain and she may want or need to shy away from you for a while.
Personally I always need time and space to get my head around my feelings before I can physically see anyone I know who is pregnant. I'm aware that this is possibly hurtful for them, and I try not to make it obvious but I have to for self preservation.
I still can't remember the Christmas that a family member announced her pregnancy (with scan photo) in front of the entire family. I had to walk away and cry on my own while everyone else congratulated them. It was the most lonely I've ever felt.
I think it's great that you're aware that this is going to be difficult for her to hear. If she's a true friend, she'll come around but it might take some time.
But definitely a personal message, either a txt (no scan photo, please, it's too painful) or a phone call, depending on how you usually conduct your friendship. I'm not a caller so if a friend called me I'd find it weird and intrusive.
Congratulations OP, you sound like a lovely friend xx