Congrats, a rescue, especially a Boxer is the only way to go. My Boxer girl was a rescue at 5 yrs. old and badly abused, a little tlc and 6 months later and she's playing with stuffed toys and after a year she was a Boxer again
In case you've never had a Boxer, IMHO, Boxers are one of the smartest breeds out there, it won't take much to train her, Boxers kind of figure things out for themselves.