Law

My friend was involved in a domestic with her ex-partner a few weeks ago. She had gone down to his work to try and sort finaces out when an argument broke out. A female colleague of her ex-parnter had walked in and started getting involved in the argument. My friend had been told that this girl had slept with her ex-parnter and that he had stayed the night. My friend was so upset by this and started to ask her if it was true. Then the argument went outside and my friend's ex-partner admitted he had and then she slapped him on the face. The female colleague had phoned the police and both her and my friend's ex-parnter gave statements. Unknown to my friend's partner he did not want this to go further and just for my friend to be cautioned. But the police arrested her and charged her with breach of the peace and assault. There were cctv cameras so the police will have seen my friend slap her ex-partner. He then phoned the police back to say he didnt want any charges against my friend but the police said they could do nothing about this?? Now my friend has to attend court tommorow and she has a solicitor to meet to go through the incident. What will happen in court and she has never been in trouble before and has a clean record. Thankyou if you could post back any answers that would be a great help. Im so worried for my friend as she is trying to cope on her own with her son and has just recently gone through spinal surgery which doesnt help.