The questions that need answering?
Did the cps treat her fairly? Why go ahead when the boyfriend dropped the charges.
The idea of someone dropping charges resulting in a case automatically being dropped is a common misconception of the pubic. Has an offence been committed?
It is not a case of a person (victim) versus the perpetrator, but rather the Crown Vs. them, so a person having to press charges is not an necessity - as above.
If the evidence reaches the threshold for them to be charged and it's in the public interest to do so, the CPS have a requirement to continue with a conviction.
The main issue is where it's the victim's statement that is the main piece of evidence, therefore if they withdraw their statement then the case becomes unlikely.
In this case, I suspect that there was evidence from them to continue to do so: it could be audio commentary, initial statement in a PB or a statement under caution.
Has she been treated fairly by the CPS? I suspect so, and if it is suspected that a crime has been convicted then they should peruse it, regardless of who it is.
Domestic Abuse cannot be overlooked and the ol' 'it's between them' stinks of people feeling that a wife/husband/finance/partner can rightfully batter the other.
They can't!