I think all you can do is say what any grieving parent would want to hear -- I'm so sorry for the loss of your child, I am so sorry for the pain you are going through.
I'm an atheist, but although I am very fortunate not to have suffered a devastating loss like the loss of a child, I know from reading and talking to other people who have suffered huge losses that -- even if they are religious -- words like "she's in a better place" or "God needed another angel" or "you'll meet again in heaven" are not necessarily sources of comfort and may even be extremely upsetting. Because no matter someone's beliefs about an afterlife or lack thereof, the truth is that NO ONE wants to lose a child even to a "better place." It hurts here and now on earth and even people of faith aren't necessarily going to take comfort in religious platitudes coming from outsiders, KWIM?
I am very sorry for your friend's loss.
: You are very sweet to try to look for resources for her, but maybe the most comforting thing you can do for her is tell her how sorry you are and try to be there for her in the weeks and months ahead to listen to how she feels and how she's living with/through her grief.
(and FYI, Buddhists are not necessarily atheists -- there are lots and lots of gods/deities/supernatural figures depending on which form of Buddhism you believe in!)