Might this be Scratch Monkey (1993) by Charles Stross?
This review provides a brief overview of the plot, mentioning a female human agent working for an AI which has created a cyberspace afterlife, called the Dreamtime:
Scratch Monkey is a far-future posthuman story featuring nanotechnology and strong AI. Specifically, it’s the spiralling narrative of Oshi Adjani, a human agent of an AI she calls “the Boss”, which belongs to a category of AIs called the Superbrights. As humanity spread out at sublight speeds across the stars, colonizing worlds in advance through the judicious use of Von Neumann probes, they used planet-sized processors to create a cyberspace afterlife: the Dreamtime. As the Dreamtime became more complex, it gave rise to AIs—the Superbrights—who have gradually co-opted it for their own survival. Humans are thriving, and in most cases functionally immortal, but their destinies are no longer their own.
Oshi begins to see through the veil of the Superbright beneficence, so she becomes expendable data—a scratch monkey. Her Boss dispatches her to a system under threat by the Ultrabrights, AIs expanding outward from the old core of human civilization whose processing power is far superior to that of the Superbrights—and, hence, they are that much more alien. Oshi’s ordered to figure out what’s happening and report back. Or, you know, die trying. Oshi’s job sucks.
The review also mentions that the book was originally a novella, which was later expanded into a full book:
Perhaps this roughness comes from the book’s origins as a novella that Stross initially did not sell then dusted off and expanded into this story. I can’t really speculate. In his afterword, Stross discusses how he’s glad the book didn’t sell when it did, because the manuscript needed a lot of work. And I can see that. The first chapter, “Year Zero Man,” which I think was the original novella, is my favourite part of this book. It’s a very satisfying vignette that shows Oshi kicking ass against fairly substantial odds, with an antagonist who sufficiently challenges Oshi’s sense of moral superiority. But “Year Zero Man” is just the prologue for the main plot of Scratch Monkey—and that, sadly, is not as interesting.
The story itself is available to read for free online.
Skimming the first chapter, the agent, Oshi Adjani, is sent to a wartorn planet to investigate the inordinate numbers of uploaded minds being sent from there to the Dreamtime:
I don't get to hear the rest. The launch rail kicks me in the small of the back and the head-up display blanks out the starscape in a blaze of tracking matrices. When my eyeballs unsquash I erase the unnecessary read-outs and take a look. The planet is a vast, ego-numbing blueness into which I'm falling. I re-run the mission profile as the orientation thrusters cut in, spinning the drop capsule so that I'm racing backwards into a sea of swirling gas at Mach thirty. The capsule is going to make an unpowered re-entry like a meteor; it's designed to pull fifty gees of deceleration on the way down (far more than any sane pilot would dream of), shedding fiery particles like a stone out of heaven. This is going to happen in about three minutes time.
I'm busy for a few seconds, heart in my mouth as I scan for search radar and missile launches, but no-one's detected me and by the time I can look up the black-surfaced station is invisible against the thin scattering of stars above me. I could almost be alone out here -- but I'm not, quite. Someone is down there: someone dangerous. Otherwise Distant Intervention wouldn't have seen fit to send a team through the system Gatecoder, fifteen light-years from anywhere else; otherwise it wouldn't have rated a visit of any kind, let alone the attention of a Superbright like the Boss. Because if nobody lives here, why the hell is it pumping out so many uploaded minds that it distorts Dreamtime processing throughout the entire sector?
Adjani does get blinded by local military police soon after arriving on said planet:
My heart is suddenly in my throat: there's an acrid taste in my mouth as my guts loosen in fear. They pick me up by the chair and carry me through the door, and breathing heavily, drop me down in front of some kind of bulky metal-box contraption and turn their backs. I try to look away but the box glares at me with two huge, violet laser eyes that suddenly grow brighter and brighter. I hear a sickening popping noise through the bones of my skull and --
I'm blind again. A haze of burning smoke shrouds the world from me; the laser has burned out my retinas and I might as well finish the job by just switching off -- nothing works any more except my Dreamtime feeds. Everything is blood-red dark, laced with the hazy nothingness of a blind spot, the scotoma. I feel a hysterical laugh building up inside. Everything seems to be very loud and I can feel the coarse ropes acutely where they cut off the circulation in my wrists. If I let myself die now, I can continue living a bit longer ... can't I? But I'll have failed, utterly. The Boss does not appreciate failures. These monsters are very good at dealing with prisoners. How can I escape, blinded in a foreign country occupied by hostile soldiers? I carefully turn my head, trying to map the room with my ears. It's hard. It's been a long time since I was blind.
She subsequently meets the woman leading the local militia, Marat Hree, who indicates that she wants no part of the Dreamtime:
She sighs. "I would have thought it was obvious. These people never asked to be farmed by your superbrights! I'm going to free them. This current generation is damned -- the nanotech uploaders are pervasive -- but if I can raise the children, cleansed at birth ..."
"How?" I ask; "I mean, why are you doing this?"
She lets go of my hand. I feel a breeze as the door opens; we're standing in a tunnel, I decide, or a lift shaft. "For love of the people," she says quietly. "The afterlife your sponsors claim to protect is a cruel lie. I come to free them from the cannibal tyranny of those who eat minds. If you don't believe me, go ask your masters. They aren't human, and their agenda is inhuman. Or did you think people were still afraid of death and upload for nothing? Step forward now." I obey, stumbling slightly on the edge, and she's behind me: the door closes and we begin to rise.
Marat Hree also speaks of her intention to overload the Dreamtime, by sending it huge numbers of uploaded minds:
"It takes a lot of stress to unbalance a network processor the size of a small moon," she replies calmly; "it shows a remarkable degree of fault tolerance. As for physical assault, the automatic defences are still armed ... as they always have been. So If we want to take it for ourselves, we must overwhelm it by frontal assault, sending uploaded minds out into the simulation space until it overloads and drops into NP-stasis. They do that if you feed them faster than they can transfer capacity elsewhere, you know. It's happened before, and it's what the Superbrights are most afraid of. A Dreamtime they lose contact with means a human world that will not succumb to their domination again. Only then will we be safe. The superbrights need uploaded minds, you see. Their intelligence needs so much input that they consume human personalities or they go insane from memetic deprivation. Overloading the Dreamtime ... you wouldn't believe how many of them it takes."