If she is bucking because she is moody and just a crank I would agree with Kevin - trails can be dangerous by themselves without adding a bucking horse to the equation. Find out why she is bucking and address that before taking her on the trails.
I made the mistake of taking a bucker out on trails.
You don't want to know the kind of horror stories my bodily injuries could tell you. Agree with the other commenters, fix the bucking, THEN go for trails :)