Through the whole video, though most noticeably in the first attempt to halt. You popped the rein up when she didn't listen, which was good, and she reacted immediately, but there was then no release. I understand that you wanted her to give, but the first aid was to stop, and when she did stop, you really needed to give her that moment of relief as a reward. She cannot understand that she did the right thing by stopping, but now you want her 'round' - she thinks it's all the same aid. Hence the gaping mouth and confusion.
Horses are simple creatures, we need to break down every aid to its simplest form. So if you want her to stop, and she stops, give her relief to show her that she did the right thing. THEN ask for the next thing.
Eventually the training will improve and she'll stay round through a downward transition, totally on your back and staying on the bit because she is using her hind legs.
I think I get what you're saying, though the first where you see her backing up was all her (in the sense that she will back up on ground and under saddle when she's PO'd)--- out of the camera sight, she started jigging, I No'd, then pulled, and she raised her nose up while still trot-jigging, I wanted a walk but with her nose up she wasn't listening, so I raised up my hands and messed with her face, in response she kept it raised but quickly went to backing instead of walking forward. The overall goal was to keep her walking, but then I wanted her nose lower so I could regain my contact, however now I'm not sure if I should prioritize differently; in the situation that she prepares to jig, starts jigging after I say No, keeps jigging after I pull and raises her nose to avoid my hand, what do I do? Should I be keeping my hands at the default position by her withers, or raising them? What happens when I keep the same pressure in the pull with her nose up, she runs through my hands entirely. When I don't raise my hands but pull again, she dives heavily onto her forehand from jiggy trot to walk and her back goes hollow. That's where I'm stuck. I still want to keep a walk when I say walk, but then I don't want her above the bit. Sometimes she goes right to backing when she sticks her nose up and I wiggle. Wiggling is the most effective thing I've found so far, I tried circling her but she sticks her tongue out and it really isn't effective in getting her to keep walking, I end up staying outside for hours doing spirals and all the turning tactics you can imagine from half-circles to serpentines.
Thanks for being pretty specific--- nothing sinks into mind for me unless I get details, and it's best for about 3 examples as ideas won't make sense to me otherwise. Sorry--- I'm a hard learner like that
** Also, she will give a cooldown walk at the end if I let the reins out to the buckle to let her stretch. I find that if I let my reins slacken too much throughout the session, she will start having more of a mind of her own, but if I put her more into a frame so that she is on the vertical with proper tracking, she won't get so antsy. I think I'm too loose with my hands, that I myself don't like to maintain a contact all that much, so the energy behind is falling out to the forehand. My trainer often says I need to "connect" her, as during a schooling trot she can get on the vertical but plod, I get the best results when I take a firmer rein and sort of square my body so I am not leaning anywhere or being passive.