(((hugs)))) I'm so sorry that happens to you.
I always say Merry Christmas unless I know the person is Jewish. There are a larger percentage of Christians than other celebrators... but since I'm only the customer, it doesn't matter what I say? I do it with a smile though and would never think to yell at someone. She sounds like she is having her own issues of the holidays, eh?
I'm glad you and your cat have made up. That's what's so great about pets...they continue to love.