What a lovely friend you are for asking. I agree with all the advice on here, and just wanted to add my own for anyone else who might be reading.
Don't say:
"Just relax / stop stressing / forget about it / get drunk and you'll get pregnant" My own gynae consultant actually said that to me
"I know someone who was trying for years and then just got drunk and got pregnant. Perhaps you should do that". Oh thanks, I didn't think of that.
"Oh god, count yourself luck you have your freedom - sometimes I wish I didn't have kids, think of all the holidays you can go on!" Yes, I love my life, but please don't patronise me
"Oh don't be negative. It will happen, I just know it". Really unhelpful. You don't know it will happen, and saying this forces me to quote the statistics showing how bloody difficult it is, which I don't really need to dwell on thanks, and then makes it seem like I'm wallowing in the negatives all the time
"Any News!!!???" No, I'm still infertile. I'll let you know if that changes
"Well maybe you're just not meant to have kids" Maybe I'm meant to throttle you with my bear hands right now
I'd say just be open to talking about it. My friends have all been brilliant, and interested and willing to listen, but I feel like I'm such a doom monger and don't want to always be talking about me and my faulty ovaries. It's great to know I can talk to them, so opening the door with "How are things going?" is great. And acknowledge that it's shit and unfair and you're there for your friend.
I also feel people tip toeing around me with other people's pregnancy news. I know they really don't know what to do, and people react differently, but I really don't want to be the person that everyone's scared to mention the PG word in front of. I'm genuinely happy for anyone that manages to get pregnant and have a healthy happy baby - I'm happy for them that they're not going through what I'm going through. I appreciate everyone's different with this one, so gauge your friend and see how she feels.