、。
She has to study hard to catch up with the rest of her class.
Literal
She [topic-は] with-all-one's-might studied-and, class [genitive-の] everyone [with-に] catch-up-must-do.
~ねばならない here in the non-past form frames the obligation as currently in force — 'she has to' rather than 'she had to.' みんな ('everyone') is the warmer, more inclusive alternative to 人 ('people'); クラスのみんな gives a slightly sympathetic view of 'the rest of the class' as a group of peers rather than a faceless mass. The comma after て-form 勉強して provides a visible clause break, common in writing for clarity. ~ねばならない itself is the formal/written counterpart of the more conversational ~なければならない.