J.B.
If she's not, just offer to be there for her but also be prepared to give her space if she needs it. And if she has a husband or partner, this may be something that they want to grieve privately. Remember that he will be grieving too - and it is grief. If she has a favorite comfort food that will keep in the fridge for a few says (soup or something), bring that too her and leave it for whenever she is ready to eat something.
My failed IVF cycle was when I was a gestational carrier. This wasn't even my baby and I was devastated and I know that what I felt, the parents felt 100 times more. There is disappointment, loss of a dream, fear that it will never work, thoughts like "why me?" and "maybe we're not meant to be parents" and "I failed (again)" and "it's my fault" and on and on.
In addition to that, she will abruptly stop taking hormones. If you remember being on an emotional roller coaster after your kids were born, she'll be going through the same thing. It took about 10 days for me to feel kind of normal, and those days felt very much like those first post-partum days, when even though I was happy, I was weepy and emotional. Add bad news on to that and you've got the makings of a very emotionally wrecked woman. So if she gets bad news, maybe in a couple of days if she's still feeling hormonal and out of sorts, let her know that that's a normal part of stopping the hormone pills and shots and that she will feel physically normal in a week or so. That was something that the nurses didn't warn me of.
Just be there for her...hopefully you'll be celebrating later though. Fingers crossed for her!