It is good that she is able to speak with you about all of this.
Be sure when she complains or acts worried you ask her, "What are you doing about this?"
" How can you solve this?"
" What do you need to make this work better?"
And the one question that always got our daughter was "Do you need me to go with you so you can talk to the teacher about this?" She did not want me talking to the teachers. It was embarrassing to her.
I can only recall 1 time she said "Yes, I want you to speak with him."
If she is not used to changing classes and lockers, that can be stressful for her.
At our daughters MS they used to spend time teaching the students how to use an agenda and how to organize their backpacks.
Also even in elementary school they switched classes, starting in 1st grade. So that part was not a big deal, but the middle school had different buildings on the campus, so being in charge of all of their supplies, was an adjustment.
The lunch room was also a huge adjustment, because you never knew who would have the same lunch period. Her "Lunch Bunch" was not always all eating at the same time, so that was always a thing that made our daughter nervous.
They did not use lockers so the students carried everything with them and the classes each had their own set of books and the students kept their subject books at home.
Also you are correct, the pace picks up in middle school from elementary school. The teachers no longer have the luxury of extending a subject or answering a ton of questions during the class period, so 6th graders need to learn to go and see the teacher before or after school to ask their questions or get their answers. the students are expected to ask for help, to seek out the teachers for help.
The teachers do not have time for any shenanigans in class, so they get right to work and expect the students to be paying attention and being prepared. They have a lot more to teach. It is my experience, middle school teachers start out very strict. They are setting the tone for their classes. The students learn good habits from the start. Some teachers will ease off a bit, but this i no longer elementary school. The students are now supposed to be prepared to get to class and be ready to listen and learn.
How is the school schedule at her school? Do they have A and the B days?
Do they switch 6 or 7 different classes each hour?
She needs to organize this so that she can get to classes on time.
Usually each subject had its own color of folder. The left was for homework that was due with the instructions, the right side pocket was for the completed homework and graded papers being sent back.
Why does she not have time to eat lunch? Is she going through the lunch line? Maybe she needs to take her own lunch. Is she visiting with her friends instead of eating? Is she taking too long to go to her locker get her lunch and trade out her supplies for the afternoon?
Have her tell you how her day goes and how often she goes to her locker. If the locker and the class are too far away ask her, what could you do instead of going all the way back to your locker?
IF she is still struggling, SHE needs to speak with her adviser or her first period teacher and let them know she is having some trouble getting to her classes etc. These teachers are used to this.
I like the suggestion of you going into the school at the end of the day and having her show you what her schedule is like within the building and how she gets to class.