you've gotten some great input here already... just wanted to say I'm so sorry to hear that your friend was in such a horrible accident... certainly every cyclists worst fear realized...

the only other thing I can say is... don't worry about "what to say"... most times you don't need to say anything... just BE there... human companionship, in and of itself, is the best support you can offer! You're a good friend to care and want to help... don't forget to take good care of YOU too... this is certainly stressful for everyone that cares for them! Hugs...