What should a female student do who – unintentionally – caused a study curriculum to become more difficult for her cohort because she informed the course professor about the many cases of cheating, in order to atone for her sin and save the future of the affected students?

We see no sin upon you in what you have mentioned, for you intended no evil nor did you commit any evil. Reporting cheating is permissible; in fact, it is a form of giving sincere advice (naseeha). What the professor did by instituting a difficult curriculum was due to the students' cheating and disruptive behavior. They are the ones who brought harm upon themselves. Whoever fails among them because they relied on cheating is not worthy of success.