It looks like there may be some changes to the entrance exams. At the moment they are consulting on the admissions arrangements for September so you may like to have a look at this thread viewtopic.php?f=24&t=45234
. So keeping in mind any changes or additional details that may arise from the consultation.
I do not think it is necessary to get a tutor. You will be looking to improve and consolidate KS2 skills in Maths and English. These skills will also serve you for verbal reasoning.
For maths -
Make sure that you have covered the KS2 syllabus by October 2016. A revision guide may be useful.
Speedy recall of times tables is going to be invaluable.
For English -
You are looking for really strong vocabulary skills. Reading is the good way to improve - shared reading and don't forget to read to her. Audio books could be useful too.
In addition you may be looking at general English skills, for instance; comprehension, writing, antonyms, synonyms and possibly a cloze test.
There are plenty of free papers to gauge how you are doing. KS2 papers. http://www.emaths.co.uk/index.php/stude ... ast-papers
You can also look at Indie school admissions papers.
She's a clever girl and very enthusiastic and hardworking at school.
These skills will serve her well wherever she goes but it is important to appreciate that not every clever child is going to qualify. Try and make sure that your child understands that this is just one of the school options available to her.
Good luck - ask if you have more questions.