Please help me identify this story.
A woman wakes up in the wilderness, with no one else around. She has no idea why. That night, the answer comes to her in a dream: Humanity is extinct, but she has been resurrected from her remains by a race that does that sort of thing.
They can resurrect the whole human race, if she asks, and if they choose to. But she must ask only once. If they say no, that's it; they cut contact with her (such as it is -- they communicate with her only through dreams, and she with them only through her thoughts).
So from time to time she lauds our species in terms of one or another thing we're supposedly good at -- technology, art, love. Each time, she receives a dream about another race, much better than us at that thing, that was refused resurrection.
Finally, as she is about to die of old age, she asks for resurrection, not for humanity, but for the race that was best at love. This surprises the aliens so much that they decide to grant the request, which they have never done before.