Not sure which exam are you talking ? We already gave 11 plus and got admit in kent grammar school.
can anybody please shed some light here
Have a look at the websites for the schools that she would like to transfer to - you are looking for 'In-year admissions' or something similar. This will tell you the procedure for applying for a place at the school in question outside the normal admission rounds of year 7 and year 12.
Unfortunately, some areas do not allow candidates who failed the 11+ to try again for a place until year 12, I believe - but if this applies, it will be stated clearly in the school's admissions procedure.
When you say she doesn't like the school, though, what exactly doesn't she like about it? Other schools may be more similar than they are different, if you see what I mean.