I'm looking for this story,
"Equinoctial", a novella by John Varley. Part of Varley's Eight Worlds series, which has a Wikipedia page.
probably published in the 80s.
First published in the 1977 anthology Ascents of Wonder edited by David Gerrold and Stephen Goldin.
In a futuristic world (~2200?, with humanity spread through the solar system) a woman who's "done everything"
"I bought passage on the first ship leaving the planet, which happened to be going to Mars. For the next sixty years I devoted myself to experiencing everything the human organism can experience and still survive.
"It would be tedious and overlong to tell you everything I did, but so you won't think I'm hiding something, I can give you a random sample.
"Drugs: I tried them all. Some only once. Others for years at a time. I had to have my personality rebuilt three times and lost a lot of memory in the process.
"Sex: with two, three, four partners; seven partners; thirty partners; three hundred partners. All-week orgies. Men, women, girls, boys. Infants. Elephants. Pythons. Corpses. I changed sex so many times I'm not sure if I grew up as a male or a female.
"I killed a man. I got away with it. I killed a woman and got away again. I got caught the third time and spent seven years in rehabilitation.
"I traveled. I went to the Belt, to Luna, to the moons of Saturn, Uranus, Neptune. I went to Pluto, and beyond with a holehunter.
"I tried surgery. I joined up with a pair-cult and was connected for a year to another woman as a Siamese twin. I tried out weird new organs and sex systems. I tried on extra limbs.
"A few years ago I joined a passivity cult. They believed all action was meaningless, and demonstrated it by having their arms and legs amputated and relying on the mercy of random strangers to feed them and keep them alive. I lay for months in the public square beneath Coprates. Sometimes I went hungry and thirsty. Sometimes I stewed in my own filth; then someone would clean me up, usually with a stern lecture to quit this way of life and go straight. I didn't care.
"But the second time a dog used me for a urinal, I gave it up. I asked someone to carry me to a doctor, and walked out a changed woman. I decided I had done everything and had better start looking for an elaborate and original suicide. I was so bored, so jaded, that breathing seemed like too much of a bother.
"Then I thought of two places I'd never been: the sun and the Rings. The sun is the fancy suicide I told you about. The only way to get to the Rings is in a Symb. I tend to sympathize with you people over the Engineers. So here I am."
undergoes body modification for zero g, and is installed within an artificially intelligent blob
The Symb was a soft-looking greenish lump in the center of the room. With the best will in the world, Parameter could not see that it resembled anything so much as a pile of green cow manure. It was smaller than she had expected, but that was because it had no occupant. She was about to remedy that.
which envelops her and uses her neurons to think. At first it's completely dumb, and she's terrified, but gradually it develops a personality and symbiosis with her.
"That's right. The Symb will do the rest. It won't be easy. You'll have between six weeks and three months of sensory deprivation while the personality develops. You'd go crazy in two days, but you won't be alone. All you'll have to hang on to will be the mind of the Symb. And it'll be a baby, hard to get along with. You'll grow up together."
They float around in space, near the rings of Saturn, where there is a population war going on between one cult which wants to turn the rings red, and another which wants to stop the first one.
"We are the loosest army in the history of humanity. We're volunteers on both sides, and on our side, we don't require that individuals do anything at all to combat the Engineers. So you don't know anything about them, beyond the fact that they've vowed to paint Ring Beta red within twenty-five thousand years."
At one point she has quintuplets which she names army, navy, air force, marines, and coast guard.
Now was one of the big moments in her life. She proposed to savor it to the full and refused to be distracted by the hunters. She was giving birth to quintuplets.
Un, Due, Tri, Quad . . . Hopelessly trite. Doc, Happy, Sneezy, Grumpy—No, there were seven of those. Army, Navy, Marine, Airforce, Coastguard? What was a Coastguard, anyway?
(Actually, the fifth child ends up being called Elephant.)
At one point she makes music and then goes back to civilization to sell it, but never does it again.
It took them four years to work their way around to Ringmarket. They traded a song, one that had taken three years to produce, a sweet-sad dirge that somehow rang with hope, orchestrated for three lutes and synthesizer; traded it and a promise of four more over the next century to a tinpanalley cat for an elephant gun. Then they went out on a trail that was four years cold to stalk the memory of those long-ago pachyderm days.