Do you mean Newstead Wood? If so it is not strictly speaking an 11+ school in the way Kent or Bucks children sit an across the board 11+. The girls sit a selective entrance exam which is incredibly tough and are then ranked. I have heard that distance from school is a factor and I think you have to be 7-8 miles from the school. They may also have music places but I'm not sure as I have a son who sat the St Olaves test so only know this info from parents of daughters in my sons class.
I have to be honest and say I think you have almost no chance of appealing for a place - in my experience you either pass and get in or you don't and there is almost no movement in the list as people choose Newstead over very highly sought after private schools such as Alleyns, Bromley High etc. Your first step would be to call the school directly and ask about the appeals process but IIRC in the Bromley booklets no-one has secured a place on appeal in recent years. I cannot think of any circumstances they would realistically consider (I know of identical twins at my sons school - one got in and one didn't
I'm sorry if I sound so depressing but the Bromley schools are quite different from areas like Kent or Bucks. I do wish you and your daughter the best of luck.