It sounds like in some sense, you do care, so in some sense, you're not cruel. I suggest you try to have a heartfelt conversation with her whereby rather than talking about her problems and negativity you talk about her potential future as a happy person. Offer her videos, music, books or anything else you can think of that helps you when you're down or that helped you get out of your depression. Advice and some kind of comfort are the best things you can offer someone in this state, it sounds like professional advice is also warranted so I wouldn't hesitate to call up your doctor's and get their advice (It's a serious matter and will be dealt with respect by professionals). She needs someone kind and considerate to be a guiding force in her recovery, in 'tribal spirit metaphorical terms' - not a rock to lean on, but a breeze to push her in the right direction

Best of luck, and if you feel you can't help / won't help for whatever reason, at least leave her with the best advice and kindness you can provide.
On a side note, judging from most of the replies you got, I don't think forums are the right place for advice on how to care for suicidal friends, most people are in their teens/20s and haven't got the life experience needed to help you.
Also, in response to SimpleThunda', I'm going to suggest that advising upon sensitive topics regarding human or animal life and care are not issues that you should ever concern yourself with. The internet may be the most democratic 'society' out there, but an opinion regarding suicide as beneficial to 'Survival of the fittest' immediately proves you a moral imbecile. I think that humanity considering it's own natural selection in such bigoted and insensitive ways is reminiscent of the rulers of Nazi Germany. Above all, if we are to progress and survive as a species we need kindness and compassion to guide our judgement, surviving as a whole is more important than stratifying the most successful genus to the top, given that we can destroy ourselves in an instant. Sorry for the rant, I thought what you said was appalling; let us all hope that rather than a callous view of life, you have an oblivious one, and will try to educate yourself further before throwing such toxic, misinformed opinions into the face of such a serious matter.