I sat her down and asked her what the problem was and just listened. She gave the usual excuses, but I just nodded, and then I asked her how she could fix the problem. She agreed to talk to her teachers the next day. I went online and helped her print out a list of missing assignments she could show her teachers, and that was that. Also, we have an agreement that she doesn't get to have her cell phone until all her missing assignments are in, so I took the phone, and since it's not the first time, it wasn't a surprise to her, and she went with it. She will get it back when they are in, and it's a little extra motivation since she is one that isn't motivated by grades.
So that is an example of how it works at our house, and I hope it helps some of you who struggle with the same things. This is a method that has worked for me and that I have developed over the years and it really works! I know from experience that if I would have let my anger take over, I would just have alienated my daughter and she would have just felt like rebelling instead of solving her own problem. So I have learned to do it better, as we all do, and I just wanted to share, so hopefully I could help others avoid my painful lessons.