You have gotten a ton of great advice, most spot on, especially from the ladies who have been through it themselves. We are going through IVF right now too; we have had two transfers, 3 embryos total between the two, and not one has implanted. It IS truly the most isolating, lonely, difficult, depressing thing I have ever done. I never thought I would be in this situation and my story comes with its own unique background, but I've learned that every person going through infertility shares the same feelings, regardless of how they arrived at the need for the procedure.
Definitely do not talk about kids/your kids. I have two of my own already so at least I can say that, but it doesn't change the fact that when you are going through IVF, babies and pregnant women are literally EVERYWHERE. You go to the nail salon to escape, there's the cover of People with some celeb and her baby. You go to the mall for retail therapy, strollers everywhere. Even the grocery shopping turns into seeing the deli people oooh and aaah over a customer's baby. This is one reason why she wants to crawl under the covers and not get up, trust me. There is no escape. Facebook is the absolute worst - if she is on it, I hope she doesn't log on often.
The best way for you to show support is to just extend your hand gently and regularly. A daily text that reminds her you are here if she needs you, a card in the mail, whatever she will tolerate. I am undecided on the food idea; while I love that it gives her one less thing to deal with/think about (I am biased, I hate making dinner!), it does seem like she could feel like people think she is sick or something. But the thing is, she is grieving the way anyone would if they lost a loved one, and this is one thing we'd do for family members who lose loved ones... so I am undecided. You know her better than we do and should make that call.
When she is "up" and a little more communicative, I suggest getting out for a walk, lunch, even a massage; anything that gets her good hormones flowing. As I have found this past year, having friends to talk to who just listen and are supportive is the best thing. I can only name one or two, but I have them and they have saved me. I also have been seeing a therapist and that has helped tremendously. I suggest that if she hasn't started already. I have never tried the group support setting but I think that would be wonderful too.
You are so kind to post this. I wish the best for you and your family members.