Trying to track down a short story set in old west at Christmas time where a woman is alone with her child and a stranger stops to help,
I am so sorry, the story sounds vaguely familiar, but I can't pinpoint the story or author. I did some searches and found some other short stories set in the old West with a Christmas theme, but not the one to which you refer. Meanwhile, I have emails out to see if anyone else is familiar with the story. I'll contact you again if someone recognizes it.
In case you are curious, here are some of the other Christmas short stories set in the in the old west that I found: