I went through this earlier this year. It is so unbelievably painful, especially when you are going through IVF, because you already feel unsure you'll ever get to a baby.
The things that helped the most were: coming over just to talk (or listen to me talk), bringing or ordering food (I couldn't even think about that and my body felt terrible) and most important to me, treating my loss as real. I felt like I had lost my baby - like losing a real person - and it meant a lot to me when friends treated my grief and loss with that seriousness. I also appreciated the cards that showed up weeks or months later.
As someone who has been through IVF, another way you can be especially helpful is being a good listener when she's ready to think next steps. In addition to the loss, thinking about doing this all over again just felt daunting. It was nice to talk people who knew the IVF lingo when it came time to decide what to do next.