I'm Anthropophobic, which is the fear of people, so I know what it's like to feel the way you do. I could never go to someones house and I can't handle people coming over to mine either. It's really hard to work around sometimes isn't it?
I think in future I'd ask for photos of the tank, ask for dimetions and ask for them to give you a guide on how they care for their Fish etc. That's what I'm planning on doing for my baby Guppies when the time comes for them to go to their new homes. The thing is (as much as it probably makes me look like a horrable person) I'm not totally trusting of people and I always want to make sure that everything is the way I like it first. And I end up asking lots of questions. I'm sure that sometimes makes me look like a stuck up something-or-other or even makes me look like a hard-a*se. But I don't mind, 'cause if people don't understand it then I know that they probably aren't the right people to become new mummies or daddies for my beloved pets.
This person promised you that your Fish would be going to a large home, clean and healthy. And that they would be well looked after. She clearly has gone against that promise. You could point that out to her along with how upset and dissapointed you are and see what she says? Show her how a tank should look and, yes I agree, direct her here where peoples could help her make it better. Or maybe she'll give you your Fish back if she knows that she's let you down so badly.
It's always worth a go. It does often work if gone about in the right way.