Charged, getting someone else charged?

I have been arrested on suspiscion of ault. The person said I hit them with a bottle (I didn't but I did hit them), however they DID hit me with a bottle (something they deny)! Both of us suffered injuries - she had a 1inch cut to the head that needed glueing and a black eye, I had a laceration to my small finger which I had to go to A&E for. Anyway - when being interviewed my solicitor told the police that we would like to press charges against the person who had pressed charges against me and we were told we couldn't. My solicitor insisted but they still refused - can they do this? My solicitor has advised me to make a complaint in writing stating that I want this person charged! It was a fight in a club both of us were at fault yet I'm the only one in trouble!!