This is tricky. I am going to try to be objective to be helpful hopefully. The text about feeling lonely at Christmas etc seems to be trying to pressurise or guilt trip sister into issuing an invitation. Bil and sister might not want a big Christmas, not want to invite op or think she should go to her daughter for Christmas day. They might then perceive the extra money as a way to "encourage" a Christmas invitation. There is no excuse for the lack of a thank you for the gift. Op it is a new year..make some plans for things which will bring you enjoyment.
Hotel etiquette - has it been forgotten?

