http://ab540.com/What_Is_AB540_.html says high school graduation with three years of high school attendance in California, or some other combination involving three years of school attendance, to be eligible for the AB540 provisions.
However, if you as the parent are a California resident, with both you and she live in California and do the usual things California residents do, then she should be able to be considered a California resident the usual way, rather than use AB540 provisions. See https://www.ucop.edu/residency/residency-requirements.html .