I have now officially read so much that I've not only forgotten what I've read, but even any reference to figure out what I've read. Here are some fragments of science-fiction stories that are floating in my mind.
Spider Assassin Lady Princess
There's a young woman, maybe she's a princess, on a planet not Earth that is kind of medieval, and there is some sort of ruling class with a prince or a king. There is also high technology, beyond anything we have on Earth still.
The young woman attends a ball or a series of events, and people are dubious about her, and she doesn't know why. She comes from another land, maybe, or her parents died young. One day, for some reason, staring in the mirror, she pushes on her stomach, and realizes there is something hard and unyielding. She continues to push and pull, and winds up removing her entire body, which is just a costume.
She's actually a spider-like, artificial intelligence-driven robot assassin whose job is to kill the king (or prince). Once she recalls her mission, she flees into the mountains, where she finds a monk. She winds up coming to terms with her identity and purpose while sleeping in a stable, perhaps? And the monk — maybe he is blind, so he doesn't know she's an AI robot spider assassin?
Anyway, eventually she winds up adjacent to the prince and then she — I can't remember. Does she kill him? Or? But she's happy with herself.
Kris Markel suggested it was "The Dust Assassin," which is an amazing story I need to read in depth! But it's not that — probably 40–60 years old, the story I'm thinking of.
Winner! It's "The Mask" from Mortal Engines by Stanisław Lem! You can read a summary of the collection of stories in that book. One of my favorite authors, and I clearly forgot having read that. Thanks, Martina Oefelein, who posted this in the comments!
Naked Lady, Dead Species
This woman wakes up on Earth and she's naked and alone in the woods. She has some memories of herself, but no idea how she came to be there, and there's no other life on the planet that she can find.
When she sleeps, she dreams of little people who were given the ability to revive extinct intelligent species. But they're kind of right bastards. They give her one chance to ask for her species to be revived, and so she's savvy and waits, and asks them about various strategies.
Here's why they're bastards. They keep showing her in her dreams all sorts of civilizations that are better, worse, whatever, than hers, but they've turned down everyone. It's like "bright shiny ball! can't have it!" behavior.
One night, she asks what happened to the race that gave them this power? Oh, they went extinct! And they decided not to revive them because they did it for whatever reasons they had, and what-ev.
The woman ages normally, and when she's near death, she makes her request. She knows they won't revive her species…so she asks that these bastards' patrons get revived. The jerks are stunned. Nobody ever made a selfless request before, and they say, "Well, we can't evaluate the reasons for you doing this, so they must be good. Sure."
But before they can revive their old buddies, a booming voice from some energy void stops them, and says the idiots finally passed their test, which was to understand…uh, how not be judgmental doofuses, I think. They take these idiots up to a higher realm of existence, and have them revive humanity and give them this god-scale power.
Not sure these patrons really think through their gifts very well.
Frozen Dead Professor Robot
This professor guy dies, but has asked to be frozen and put into orbit. He is. Unfathomable time later, intelligent robots arrive, but everything on Earth has worn away into dust, and only dead frozen professor guy remains. They revive him, and stick his brain into a robot body, and then I believe they have a series of adventures.
This is almost certainly "The Jameson Satellite" found in Before the Golden Age: A Science Fiction Anthology of the 1930s, because I've read that book! It's really interesting to see what sci-fi was about before all the tropes became cemented into place. Thanks to Patrick Last Name Withheld!