Employers can often change the start/finish times of working hours to suit but increasing/reducing hours is a different matter. She has a contract of works X hours and gets Y money. The employer can consult with staff over changing hours but its not an automatic right. Even if they did try and push it through they would have to give her notice, and she doesn't have to accept. She could force the issue and refuse, in which case they might make her redundant (and pay up). Depends on what she wants from the career / job I guess.