First, let me tell you how good it is to know that some parents like you actually go to the trouble to check first before turning their kids over to anyone with a good sales pitch. If all of our parents had taken this kind of responsibility, none of us would have been abuse. Your daughter's a lucky kid and I envy her.
If your daughter is acting in a way that tries your patience, think of how much harder it would be for you to not lash out at her if she were just a stranger; someone else's kid who you had to put up with because you're being paid to put up with her. Even good people can be cruel sometimes.
Think about what the term "Behavior Modificaion" means. There's only one way to change someone's behavior against their will. You have to break their will. I think that you could go on and on checking into 'schools' that promise behavior modification and you'd only find that one after another uses psychological and/or physical abuse to accomplish it. Either that, you'll just get worn down by the process and land up running into someone with an especially good sales pitch at a time when you're especially vulnerable and just go with it.
I think the other two posters gave you some good advice. Not something I would have thought of. I hope you'll consider some more options as well. Does she have any other family that would be willing to have her visit for the summer? Sometimes, just a change of scenery and time away from a complex situation can give a kid the chance to figure things out, maybe to talk with you or someone else she trusts about what's bothering her.
One more thing, something my dad told me after the Program and we both had come to realize how messed up it all was. My daughter had been acting out, arguing, being hostile and dissobedient. I think she was about 12 then. I asked my dad how long it takes kids to get over it. He said "Till they're about 35" I was about 30 then.
I wish the three of you all the best. Please drop back and let us know how it works out.
Climb the mountains and get their good tidings. Nature's peace will flow into you as sunshine flows into trees. The winds will blow their own freshness into you, and the storms their energy, while cares will drop off like autumn leaves. When we try to pick out anything by itself, we find it hitched to everything else in the Universe. -- My First Summer in the Sierra , 1911, page 110.
http://www.amazon.com/exec/obidos/ASIN/0395353513/' target='_new'> John Muir