Without more details about the particular new Christmas story, it's impossible to determine who the mom is. It could be a completely new character created for that story, or it could be a reimagined version of a traditional character in a new context.
I'm not sure specifically who the mom is in this new Christmas story without more context. It could be an ordinary woman with a big heart for her family and the Christmas spirit.
Mom in the new Christmas story could be anyone from a young mother experiencing her first Christmas with a new baby to an older mom who has been through many Christmases. She could be the one who spreads love and joy, from helping the kids write letters to Santa to making sure the grandparents are comfortable when they visit for Christmas. She is the glue that holds the family's Christmas celebration together.
Since we don't know the particular 'new Christmas story', it's difficult to say exactly who the mom is. However, often in Christmas stories, the mom is a central character in creating a warm and festive family atmosphere. She could be busy wrapping presents, baking cookies, or reading Christmas stories to the kids. She represents the nurturing and family - centered aspect of the holiday.
I'm not sure who plays the mom in the new Christmas Story. You might want to check the official cast list or recent entertainment news for that information.