I think the best thing is to be honest. Just say to them that you don't know much about it but that you are there for them to talk to if they need it. I think she would be impressed to know that you are trolling IVF forums to try and find out some info for yourself too.
General rule of thumb, if it's a cliche, don't say it. And remember that sometimes us IVF folk like to be a bit negative, when I am cycling I am always saying that it won't work and hunting for AF symptoms and as such. Don't necessarily agree with her or reinforce what she says, but don't try and be positive or make her "feel better". Just be there.