I am not trying to attack you, I am trying to convey to you the severity of this problem.
I would also like to point that saying she had no problems in a previous home doesn't really count if she was only a puppy at the time...most agression problems occur as dogs reach maturity and start pushing the boundaries. Whether or not she's agressive to people now, she could still accidentally bite somebody breaking up a fight. I know people whith small dogs who have been severely bitten when they lifted the small dogs above their heads to save them from an attacking dog.
I'm glad that you're getting a trainer for her, and I sincerely hope that it all works out. Boxers are a great breed in general and I'd hate to see one get put down if it can be avoided.