These people aren't really her family.
They're Melanie's.
Only she knows everything about them, Jamie's first word and first steps, the first time Jared kissed her and the first time she kissed him, sitting on Uncle Jeb's knee as he told her stories about aliens and magic, whilst her mother told him not to make up such silly things.
It turned out that he was right.
But those weren't her memories, they were the body's. This wasn't her family.
And both sides know it. The person that has come back to them is not their Melanie.
It is the thing that has taken her over.