Best suggestion I can offer is to get your DD to borrow some different size/weight/manufacture bats during practice and try them out. This is not a "one size fits all" scenario. Hard to go wrong with any of the major manufacturers and a lot of them will be releasing their 2016 models in the next month or two if you can wait. When you are ready to buy check with Coresoftball20 and he will hook you up with a great deal.
^^^^^^^ This. ^^^^^^^
The only thing I'd add is that I try to get 'em to a 32" -10 as soon as they can possibly handle it. Once they're there, the moving up in size slows way down and it isn't uncommon for a girl to use a 32" bat for two or three years.