Dear L. A,
What I am about to say is just for you, not for your friend. It is very sweet that you are concerned about how to support your friend. In these cases, we need to understand what frustration is, "to keep wanting unrealistic expectations." Once we understand this, we need to accept reality. Once we accept reality, we start coming up with a plan about how to deal with it.
This is the point where you are at right now, however, your friend is a step or two behind. She still needs to accept reality and come up with a plan to cope.
As a friend you, can call her a couple times a week to ask how she feels. This will show her support. In one of those conversations, you might want to suggest to adopt a baby. Adoption is such a noble act of kindness as it gives the opportunity for a baby to have a normal life within family bonds.
Trust me, even with my own kids, I have had problems with anxiety disorders with one of them. I know how important it is to raise kids properly and be able to discipline them and love them at the same time. Adoption must not be taken lightly. If your friend and her husband decide to go that route, they should take their time to choose the baby they will adopt and prepare themselves to be ready for this special baby that will join their home.
The preparation for being a parent will give your friend hope and she will be able to see life in a different way instead of focusing in failure as she may feel at this moment. Things like this happen to us in life. We need to learn and get the most out of the experience instead.
Hope this helps. Thanks for being such a good friend!