The Evil Grandma
Sometimes, it doesn’t matter who your biological parents are- your family is the people who are always there for you. This girl grew up with her mother and her new husband as her practical father; even though he wasn’t her biological dad, he was always there by her side, and she grew up thinking of him as her dad.

We don’t see what the big deal is if she called him “dad” and his mother “grandma”- they might not be biologically related, but they act as a family! They spend Christmas together, after all, which says a lot. So what if she isn’t technically her grandma? Honestly, she sounds like a mean, bitter lady.