i know nothing of this diagnosis- but think the best thing you can do is let her cry if she needs to- ask her what she understands of the condition- and as said by another- find out a bit about it yourself-
for me - i have 1 diagnosed with AS (autism) and another i think has it to- the worst thing people say to me is ' all kids do that' when one of them have a 'difficulty'....now i know that doesn't apply to your friends child- but the point i'm making is that i would mostly rather people stop trivialising my son's difficulty- and on the other hand not over do the 'sympathy' either- it's a very 'fine line' between the two extremes and only a true friend can get the right balance!
The fact that you have posted here shows you are the kind of friend we could all do with!
My biggest bit of advice is that she will be feeling a kind of grief at the moment- the shock of any diagonosis is so 'final' (even if it's something you knew deep down was likely to be confirmed) So she will go through stages of anger,guilt and fear and she needs to know that it's OK to feel all those feelings.
Below is something i've posted before which was written after a woman gave birth to a baby with Downs Syndrome- maybe you can take it to her in an envelope and she can read it when she feels stronger.
Welcome To Holland
by
Emily Perl Kingsley (following the birth of her son who has Down Syndrome.)
c1987 by Emily Perl Kingsley. All rights reserved.
I am often asked to describe the experience of raising a child with a disability - to try to help people who have not shared that unique experience to understand it, to imagine how it would feel. It's like this......
When you're going to have a baby, it's like planning a fabulous vacation trip - to Italy. You buy a bunch of guide books and make your wonderful plans. The Coliseum. The Michelangelo David. The gondolas in Venice. You may learn some handy phrases in Italian. It's all very exciting.
After months of eager anticipation, the day finally arrives. You pack your bags and off you go. Several hours later, the plane lands. The stewardess comes in and says, "Welcome to Holland."
"Holland?!?" you say. "What do you mean Holland?? I signed up for Italy! I'm supposed to be in Italy. All my life I've dreamed of going to Italy."
But there's been a change in the flight plan. They've landed in Holland and there you must stay.
The important thing is that they haven't taken you to a horrible, disgusting, filthy place, full of pestilence, famine and disease. It's just a different place.
So you must go out and buy new guide books. And you must learn a whole new language. And you will meet a whole new group of people you would never have met.
It's just a different place. It's slower-paced than Italy, less flashy than Italy. But after you've been there for a while and you catch your breath, you look around.... and you begin to notice that Holland has windmills....and Holland has tulips. Holland even has Rembrandts.
But everyone you know is busy coming and going from Italy... and they're all bragging about what a wonderful time they had there. And for the rest of your life, you will say "Yes, that's where I was supposed to go. That's what I had planned."
And the pain of that will never, ever, ever, ever go away... because the loss of that dream is a very very significant loss.
But... if you spend your life mourning the fact that you didn't get to Italy, you may never be free to enjoy the very special, the very lovely things ... about Holland.