She should steer clear of lifting that is directed to bulk-up the muscles in the fingers, wrist, arm, shoulder and back. This type of muscles will slow her down. She needs to develop 'Quick Twitch' muscles AND to develop a balanced set on both sides (not just her pitching arm). She is not playing football and being muscle bound is to no advantage. Core strength and leg strength can be improved by the more traditional lifting programs but spinning the arm faster, snapping the wrist faster is NOT helped by traditional lifting protocols.
Remember that most 'Fitness Centers' are staffed by male lifters, their agenda is not conducive to female pitchers getting faster. Be very careful here, especially with the younger pitchers. The running machines seem to be safe and useful. The leg machines are probably the same. Be wary of lifting excessive weight overhead. At all costs avoid injury to the shoulder and back areas. These areas are getting a lot of work form the simple act of pitching. You must strive to avoid injury, any gain will be lost.
I would tend to focus on rubber band work, a Finch windmill.... perhaps a weighted sock..... Things that are quick and then rest. Stay away from the barbells, bench press type machines, most of the machines that exist in the traditional football weight room.
I would be interested in what other exercises have been found to actually work.