My DD is just about to complete her first year at Kendrick (goodness that went fast!). She started doing practice tests shortly after starting Year 6 and did approx 5-6 practice tests/week until about two weeks before the exam when she did at least one VR and one NVR test/day. We used Bond and NFERNelson practice tests and initially just worked through the practice papers to see which sections she struggled with, and then focussed on those. She didn't have a tutor because I felt pretty strongly that if she needed a tutor to get in she may struggle with the work once there . . . but if you have a DD who needs test-taking coaching I can see the sense in tutoring.
At first, my DD struggled with getting everything completed w/in the time, but once she got accustomed to the shape and structure of the test, her timing improved, as did her scores. We charted her scores so that she could see her progress and see what she needed to spend more time practicing (with her it was VR stuff). By the time she took the test, she was consistently getting in the 90s (percentage-wise) in her practice tests.
On the day, she completed the test w/in the time and came (joint) 46th . . . I'm afraid I have no idea whether girls who didn't complete got in.
As for whether you should put your DD forward, only you know your daughter well enough to answer that
We struggled with this too initially . . . but after talking to her we realized that if she didn't get in she wouldn't see herself as a "failure." She understood how tough the competition was and, while after visiiting the school she really wanted to go, she went into the test being very realistic about her chances (no guarantee). I would never have put my older DD forward, though, not because she isn't bright enough, but because she would have put herself under undue stress and pressure, which I felt was unfair on her.
If you do decide to put your DD forward, I wish you both (all) the best of luck . . . and please let us know how she gets on. I know it all seems daunting, but it's probably harder for the parents that it is for the children. ****** was very sanguine and grown up about the whole thing, while I was a nervous wreck waiting for the test results!