Texas standard possession rules for the non primary parent over the holidays question/?

The rules state that the other parent is supposed to come and get the child by 6pm on the day they are released for Christmas break and return them by the 26th at noon in even numbered years. This is our first year, we just won custody of my stepdaughter earlier this year that she would be techinically going to her moms. Wednesday (tomorrow) is the Christmas break release date, and she is supposed to get her at 6pm from our house. What happens if she doesn't get her and wants to try and wait till Thursday or Friday is she still legally entitled to her or not since she didn't get her on the time and date specified. And yes we are sticking to the paper work, obviously everyone knows its hard for a dad to win custody from a mom unless she was in a bad situation and she was, so we are not wavering on this.... Thanks for the help!