The nurse who tells Heather about Cat's blood says that a child's blood would have some kind of identifier that is the same as the parent. This is not true; offspring can inherit blood type from either or both parents and will not necessarily match them both. Additionally, they would have tested her blood type before taking her blood to have in reserve for her father. And for the nurse to tell Heather about Cat's blood is a huge HIPAA violation and would not happen in a scene like this.