There's a good leaflet on the miscarriage association website, aimed at friends and family.
The people I found helpful were the ones who just let me be sad - they asked questions about the baby, about how I was, how my DH was, ie they treated it like a normal bereavement.
Also bear in mind that physically there's a massive blow to the body, I was exhausted and very hormonal for a few months.
You're right not to say anything about trying again. I had so many comments from people that we could try again, at least I knew my dh and I could conceive, I already had the maternity clothes so would be ready for next time etc etc. it's like they wanted to cheer me up, sort of "look at the bright side", but it was the saddest period of my life and it just made me feel like they didn't understand or care.
Please help me so I can support her. What is the best thing someone did for you or said to you? She's quite a driven competitive person and this is clearly going to hit her like a ton of bricks. (Not that it wouldn't do that anyway IYSWIM!) I don't want to hassle her by texting all the time but I want her to know she's not got to deal with it on her own. Any suggestions gratefully received. Clearly, I'm not going to be insensitive and suggest she can try again etc etc.....