Actions against the police for failing to record a report regarding an assault on my daughter who was a minor when this happened

My daughter who has learning disabilities and was 17 years of age when a person in a position of trust, whilst on a residential trip away assaulted my daughter. This incident took place in September 2105. My daughter only disclosed what happened to her in September 2016, it was reported to the police and my daughter and I even had a meeting with a Superintendent and he told me that it was not assault and that was the end of it. I have fought for over a year to obtain answers from the police and was getting nowhere. Eventually, an independent  DI from an out of area force re-looked at all the reports and his findings have clearly shown that it was common assault and should have been investigated as that but also it transpires that it was not even logged on the police system. This is what I have been sent and

it should have been reported as a crime at the time and investigated thoroughly. I can only apologise that this did not occur. Unfortunately, this is not something that we are now able to recover because there are time constraints in which we need to bring a prosecution for offences of common assault (6 months) and as we discussed, we are now outside of that time limit. Again, on behalf of xxxxx xxxxxxxxx Police I would like to apologise sincerely for the lack of action taken in relation to this incident.

What can we do to get justice for my daughter?  An apology does not give my daughter the life back that she has lost due to this and her mental health will never recover from this. Please any advice?