Presumably you have done the journeys to and from both schools, during rush hour to make a comparison? And you are confident that you live well within the catchment for the Holt (we know people who are in catchment but still too far away to qualify for a place)?
With your DD's score, personally I would put Kendrick down as first on the CAF followed by Holt. As Tinkers rightly says you can't change your mind for Kendrick later on.
As a yr7 Kendrick mother, I have been extremely happy with how well my kids have settled in. According to them, ALL the girls are nice. They have 2 hours of PE per week plus numerous after school sports clubs, here's a link to the clubs list, it looks fairly up to date http://www.kendrick.reading.sch.uk/student-life/clubs/
Plenty of girls start without knowing anyone else. I was surprised that most of our classmates are from the Reading area, I think in each class there is a handful from further afield - they take trains or are driven. The ones on public transport seem to really enjoy it.
We have yet to experience the joys of a joint disco with Reading Boys