How can I encourage my girlfriend to complete her homework?

My girlfriend (19F) has ADHD and depression, which makes it difficult for her to balance work, life, and school. She really needs to socialize to help stave off her depression, and I completely understand that. However, she often has trouble completing her homework or work before going out. As both of us are in college, there are plenty of opportunities for her to spend time with friends, and while she intends to buckle down and finish her assignments first, she usually doesn't follow through. She's fallen behind on assignments from weeks ago and sometimes fails to meet deadlines, even for those extensions she receives on overdue work. When she feels overwhelmed, she tends to shut down entirely and can't seem to tackle anything. Before the Spring semester began, we discussed ways I could help her find a better balance. She suggested it might be helpful if I asked her, "What assignments do you need to finish before heading to the party tonight?" but occasionally she brushes off those reminders. I find myself getting stressed when I see how behind she is with school and her work commitments. I'm unsure if I should be this concerned or what I might say or do to truly support her. It worries me when she expresses feeling overwhelmed about her backlog. Any advice would be greatly appreciated. Thanks in advance!