I'm sorry to hear that. Poor kitty. But it's kind of your neighbor to do that for her, much better than letting her die alone and cold. (And btw it's awesome of you to let Buster in! I'm sure he appreciates that.)
I had two stray friends who would hang around my apartment and follow me around the last few months, but I haven't seen either of them for weeks now. I know some people in another building would feed and visit them though, so I'm hoping one of them adopted the cats or took them to a shelter so they wouldn't be cold. I especially hope the orange boy I was so fond of is safe. ;__;