This is something that is constantly asked and wondered - you would think there would be a list, either a requirement for the prisoner to add who they are expecting/allowing to visit or a sign in sheet of who comes and goes. I don't know if we've ever been able to confirm if they had this the year/month WCJD attempted going.
If the time is accurate that she was estimated to have left Hithin Post, I don't think she made it to the prison. That's just too late in the evening/night where I think she would've have just opted to try and make it the next day or it would've been closed for visitors by the time she got there (given the assumption she was visiting an in mate and not an employee).