Many freshmen go through this. They are in a college with a whole bunch of kids who did as well as they did in high school. Suddenly, they aren't necessarily at the top of the heap. College professors expect students to be independent, and they don't give as many daily homework assignments that are turned in and checked. Professors expect students to do the reading whether there's anything to turn in or not. Often there are fewer quizzes/tests so kids don't realize they aren't up to par as early in the semester as they did in high school.
Also, professors expect students to assess themselves, and to ask for help before things slide too far. That means your daughter should go to professors during posted office hours, or at least ask after class when she can have a conference.
Your job is not to get involved with the college or professors. Most schools don't even allow that. You should encourage her, tell her this happens to many first year students, and remind her that the college's and the professors' desire is that she succeed. They are not in the business of accepting students who will fail - it's not the goal of educators anyway, but it also would be a very poor business decision because it's expensive to bring kids in and then boot them out and have to recruit transfers to replace them. So help assure her of their willingness to help. She should show some initiative and figure out ways to make up the work - she can take a summer class a few times, perhaps, and maybe get an incomplete or two instead of a failing grade. She should investigate academic support services that the college offers. But she has to take the initiative to ask and to say she wants and will accept the help.
If you think she is suffering from depression and requires treatment (counseling, meds or a combination, even short-term), then you should encourage her to speak to someone. Since she has a history of self-esteem issues, but you don't say what you mean by "she's working on that," so I hope that doesn't mean she's doing it alone. Maybe she needs a counselor, maybe she needs a life coach to get her fired up and in touch with her many strengths. It's okay to lose one's way, you know? One just has to be willing to work with a map and a navigator to get on track.