I have not written publicly about this because I was so ashamed of my tactical error and so worried about the cat.
On January 9, I spotted her in a vacant lot a few blocks from home. "Mia! You're NOT DEAD!" She remembered me and did not run away. After feeding her for a two weeks and receiving many happy purrs and cuddles, I was able to trap her last week and bring her home to my own apartment, the one with less traffic and more control of windows.
This time, Mia seems delighted to be indoors with a reliable food supply and cuddles on demand. What changed? Well, it's winter. And the other cats are nicer to her than the ones at Dad's. She is becoming good friends with Blackie. Rosebud hisses at her but is too old and fat to chase her. Pixel just ignores her.
I feel like a mountain has been removed from my shoulders.