SciFi/ Fantasy. Girl has small robot helper called a savant. Matchmaker finds genetically compatible people (may live a great distance away). VR RPG-like way to communicate with others in virtual computer world? People disappear in mists. Read before 2010.

[Midnights]

Year read: pre 2010 checked out from a public library.
Cover: was likely mostly dark colors, I think with a lighter colored arc on it. likely mist on there. I'm not great with visual memory and you know how grody library plastic covers on hardbacks can get.
Read west coast united states but a friend in the UK may have read it too as it sounds familiar to them.
I can't remember the author's gender.

Plot/world:
A girl was the main character. She had a small robot called a savant. This is where I learned that word actually. Pretty sure the bot floated. I'm pretty sure it appears in the first few pages.
I believe people lived a great distance from each other. To form relationships, a matchmaker was consulted to make sure they were genetically compatible. Kinda post apocalyptic in the sparse humanity, reproduction is hard aspect.
I think she used some sort of virtual world to go to a "town" with other people. very early internet style concepts though.
There were mists that came on some nights. I think they disappeared people rather than killing them.
The setting gives deserty rocky vibes. She didn't live in a town. She was an explorer type.
I think there was some familial thing that an older brother or a father had gone missing, possibly in relation to the mists. The plot might have revolved around what the mists were.

On a side note, I was positive I had added this thing to a goodreads list because I have accidentally re-read it and canNOT remember the title. But apparently it's not there. No it's not Iona whatever. God no. And don't read that. Last time this happened I Google searched it so I could find it, but now all I get is Mistborn and Mists of Avalon and 5 ways to tell if your child is a savant :/.
Any help is appreciated!

[Kris]

Midnights, is this book for adults or teens?

How does the robot (savant) help the girl? How old is she?

I added few details to the header/ topic title. Feel free to edit it.

[Sue]

I think this could be Memory by Linda Nagata.

The mists you remember are called Silver.

[Kris]

Sue's suggestion of Memory by Linda Nagata looks very promising. Amazon has a short "Look Inside" preview:

https://www.amazon.com/Memory-Linda-N... There are different cover images including

Quote from book:
"Under my direction the savant surveyed the folly, recording both the carvings and the gateway from every side while Liam make jokes about what the symbols might mere. "This column here," he said, pointing to stacked symbols on the inside of the gateway, "means 'give us a kiss and you can go past.' "