A Job that my fiancée applied for has been taken by someone on redeployment after the application date closed.

Hi, my fiancée has just lost a job opportunity for a radiographic assistant in Mammography that only she has applied for as it was an internal job opening. She has been working on bank for 1 year in Mammography and enjoys it the most out of her other job roles. She made a fantastic impression on the staff in the last year and her line manager and co-worker were looking forward to having her working with them full time. 

But today she found out someone on redeployment has taken her potential job without needing to apply for the job or completing an interview and missing the deadline for a job the person on redeployment hasn't even applied for. Her line manager today broke the news explaining that the person on redeployment has taken her potential job and there isn't anything they can do about it to stop it. 

Her line manager has contacted work force to try and find out if there is any way to stop this from happening, and explained line that my fiancée has been working the job for just over a year and is a perfect candidate, but they replied that it not possible to stop this from happening and the job must be automatically given the person on redeployment. The line manager also told my fiancée that the person on redeployment has had their union representative email her specifically as she has been trying to find out information and try and stop this from happening. 

For clarification my fiancée is clerical staff Monday, Tuesday. Radiographic assistant, Wednesday, Thursday, and 1 day radiographic assistant in Mammography on a Friday. 

She's pretty upset at the moment because it feels stolen and pretty much out of nowhere and she's been trying her best to make a good foothold there and further her career in the Mammography department.

If anyone could give any advice on this situation that would be fantastic and much appreciated. Thank you.