Aside from the lines, I'd be careful not to buy something with enormous, flash paces. Yes they look nice and may be quite talented, but a young kid would have a hell of a time trying to put such a horse together.
How serious is your daughter about Dressage? Is she at a state/national level as a young rider and wanting to be competitive? If not, you can pick up a nice small schoolmaster for reasonable money. It doesn't HAVE to be a warmblood. A well trained tb is worth it's weight in gold as well.
Warmbloods are generally not the quiet, dopey autopilot beasts they can be made out to be. As fond have said above, there are certainly lines that can throw very tricky temperaments. I'm a competitor at state level and have had experience bribing on a wide range of horses but I'm still wary of the Jazz line among others. In Australia Sandro Hit is immensely popular, he throws phenomenal paces but they can go off their rocker at the drop of a hat. No Thank you!!
Find something with a good brain, 3 nice rideable paces and a back that wants to swing naturally and you'll be well on your way.
By the way - I hope your daughter knows how incredibly lucky she is having a parent willing to pay some money for a quality horse. As a pre teen I was still saving my $2/week pocket money so I could buy my first pony, some scrubby bush pony ridden a handful of times in her 12 years and popped out a few foals!!
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