She needs to be logging everything that goes on, dates, times, what's been said etc.

Get her to join the unite union, they cover shop workers etc. She needs to let the manager know she is being bullied, otherwise they will say they were not made aware of the situation, and didnt have time to sort it out blah blah.

There will be people at unite that will help her deal with it, and will sort it out. Most companies will have procedures in place for bullying, but they very rarely follow them. It would be worth following it through even if she leaves, would be a confidence boost to her knowing that she was able to tackle it rather than 'run away'.
Things like this really piss me off.