She should borrow/rent a zoom like the 16-35, 24-70 or the 24-105, go out shoot a bunch shots and then look at the EXIF and see what mm she seemed to shoot at most and then buy the corresponding prime lens.
She should borrow/rent a zoom like the 16-35, 24-70 or the 24-105, go out shoot a bunch shots and then look at the EXIF and see what mm she seemed to shoot at most and then buy the corresponding prime lens.