The Christmas Catalyst

What can a ten-year-old girl do to improve this Christmas when her father will never be with them for Christmas again?

Christmas without him seems bleak, so she tries to befriend a homeless mutt, which her mother won’t let her keep. Then when she takes her grandmother to meet the man who moved into the cabin in the woods behind them, she finds he has adopted the dog which makes her happy. But why does her grandmother sort of adopt the man, inviting him for Christmas Dinner?