Is she a junior?
If affordable, a private tutor is probably best…but do get recommendations for good, experienced ones in your area, whether in-person or via Skype/Zoom. Next choice would be to do the (free) prep and studying on Khan Academy, as noted above…but your D has to be sufficiently self-motivated to make that a real option.
Your D will not only have the tutor/Khan session(s) each week but also homework, so on top of school work and any ECs, efficient time management is necessary.
I would also have her sit for a real, timed test…typically many tutor companies offer these, sometimes at the same site as the real test, a weekend or two before each test for clients and non-clients alike.