The test can give false positives, so she goes back in for the Western Blot retest tomorrow.
What does this mean? I don't really know. The vet proposed for the second time that I might want to have them terminate her pregnancy (... oog). I was kind of freaked out at the time he gave me the diagnosis, but based on about two minutes of websurfing, I think this might actually be manageable. Transmission is low, primarily via blood drawn when fighting, so Chess and Butler should be fine (although Chess managed to slip past me and get a faceful of enraged Daisy about 15 minutes before I got the test results, so she'll need to be tested herself in about six months). Since she and her current kittens and her maybe-more kittens will all get fixed and will all be kept indoors, their prognosis should be quite good. (The shelter auxiliary woman seems to be under the impression that kittens with FIV won't make it to a year old, but she's going to talk to their vet about that.) It's not certain that the kittens do/would get it from her anyway.
But FIV does make cats harder to place. In addition, Daisy may have parasites (testing in progress) and she may have a heart murmur.
On the other hand, she's survived on the streets for at least two full years. (The vet estimated her to be a year or two old, but since she had another litter under my house two years ago, we're guessing he was a bit off.) She seems to be in good condition, especially now that she's getting fed well and regularly. The kittens also seem fine.
I don't know if the potential foster would still take Daisy and the kittens. The shelter auxiliary woman thought that the kittens wouldn't survive, that Daisy might not be able to cope with people, and that Daisy wouldn't handle crating. I pointed out that Daisy wouldn't need to be crated for several days at her house; she can stay at my house and then be transported directly to a foster via regular carrier, which she can cope with. Then I had to explain to her that Daisy is just fine with people who don't talk loudly at her while lunging at or grabbing her (which she and her associate did the whole time, though I didn't stress that point). Both of them deal with hundreds of cats; how do they not know that you approach any strange cat slowly and let it sniff your hand and wait for its permission before touching it? Then again, the associate handled Daisy and the kittens and then went straight over to rub her hands all over Chess when we had no idea whether FeLV was a factor, so ... let's just say I'm not overwhelmed by their expertise.
But now that we don't necessarily have to take full quarantine measures between the "downstairs" and "upstairs" cats, Daisy and her two-plus-N kittens can hang out in the basement until they find a better home. We'll see what happens.