She should take those where the subject credit (fulfilling requirements and advanced placement) will be useful for her. That may depend on her major as well as the specific campus.
However, if she intends to repeat the course in college for pre-med grade-boosting purposes (most commonly done by pre-meds for physics, biology, and/or general chemistry), it is best not to take the AP tests in order to avoid the possibility of having to mark that the course is a “repeat” on the medical school application. You may want to ask in the pre-med forum section any pre-med specific issues (there are some regarding AP credit).