Dona - don't beat yourself up please. I know you must be in a "funk" right now, but I truly feel that the holiday season makes it seem even worse. I get extra "down" this time of year over things that don't normally bother me as much at other times.
I'm divorced (and happily so) and also estranged from my oldest son, but even so, I miss what used to be. I get very blue remembering Christmases past, as a big, happy family - even tho I have my other son, DIL, and grandkids around all the time. I don't let them know how really sad I feel, since I want to create happy memories for them to have when I'm no longer around.
And unfortunately I know what broke feels like too, since Uncle Sam and his social security payments don't amount to a hill of beans, compared to what I was paid when I was working.
I know it's easy for me to say, but you did right by your friend, and hopefully she'll do right by you!
And so sorry about Callie, but I wonder if she could have been saved anyway since it seems that she went down hill so fast. Perhaps there is nothing that could have been done, even if she had been taken to the vet sooner. It's not your fault - God knows that you do sooo much for kitties!
Try to feel better - go look at a pic of Josh Groban!!!