A few things to consider:
Is this her first year in middle school and having multiple teachers? If so, adjusting to the increased organizational challenges of handling multiple classes and teachers with different homework/etc approaches can be tough at this point for most students. We've found through middle and high school that our kids typically have a mix of teacher styles re organization: some teachers purposely structure how they assign work and how they expect it to be turned in in a way that helps students meet the demands surrounding organization, teachers that seem to assign things fairly randomly and don't see that they have any need to help students learn/practice being organized... plus usually one teacher per semester who's just naturally completely disorganized themselves. Some subjects naturally lend themselves to easier homework organization too - math, for instance, where typically a class studies from one book all year and completes assignments from the book sequentially and students expect to have homework each night.
So the first step I'd suggest here is to look analytically at which classes your dd is having difficulty with getting assignments turned in, then talk to her about what's required: how are assignments given out, how are they turned in, how often does she have homework in that class etc. Also look at how she keeps track of her homework assignments - is she writing them down somewhere? In individual class notebooks or in a planner or other? If she's feeling sensitive about the classes where she's missing assignments, you can instead look at her full day together - how does each teacher assign homework etc... make it less of a "how to solve the problem of missing assignments" and more of a "how to manage planning" exercise.
I've found that giving my kids a lot of organizational support at home during middle school and the first year of high school really helps them learn how to be organized in their own way. The level of help required really depends on the individual student - one of my kids has a disability that impacts executive function, and we worked on org skills together all the way through middle school and quite a bit freshman year of high school. He's functioning fairly well now as a junior in high school, but we still check in daily and he still occasionally needs someone to help him with strategies for planning long term assignments etc.
Re what I actually did/do with my kids: I ask them to tell me about what they did in school each day when I first see them after school. I want to hear what they did in each class as well as what homework assignments they have. None of my kids really wanted to do this when we first started, but I explain to them - it's not because I'm trying to look over their shoulder and micromanage them, it's because they're my kids and I am naturally interested in what's going on in their day when they're not with me. We repeat this "tell me about your day" exercise everyday, and it has benefits beyond helping me support them through organizational challenges, it's helped them realize that I expect to continue communicating with them through whatever goes on during the teen years
Since it sounds like your dd is at odds with you over this, is there another adult in her life who could talk to her about it? Someone she's less emotional and dramatic with?
Last thing I wanted to mention - ADHD isn't the only thing that can cause executive function and organizational challenges. You've mentioned in your other posts that your dd appears to be making a lot of sign errors and mistakes in the "easy" parts of math calculations but grasps math concepts easily. I doubt this is what's happening, but I'd keep it in the back of my mind and pay attention as you work with her on the math and the organization challenges - these could be related to each other and possibly an undiagnosed LD that's mild enough she's been able to cope up to this point. Again, I doubt that's what's up - but it's something to be aware of.
Best wishes,
polarbear
ps - there's a book put together for ADHD that helped us a lot in middle school with organizational challenges for my ds (who doesn't have ADHD, but had tremendous org challenges).. I can't remember the name at the moment (ha! I must have my own challenges lol!).. but it was something like "Lost and Scattered"... anyone else who can help with the name? It's a short book with lots of great tips.
pps - one last tip from me
If she's doing well with organization in classes where the teacher and homework are well structured, be sure to encourage and celebrate that - those classes were (I believe) really important for my ds in helping him learn how to develop his own organizational system and they helped him see he could be successful at managing homework.
