Not sure if this is just me, but it does look to me like your saddle is too forward? Idk, I can't really tell, but it's just a thought.
Shorten your stirrups and go back to the trot, like others have suggested. She is hollowing her back and sticking her nose in the air (most green horses do this, it's normal). Work on transitions, do figure8's, serpentines, etc. Once you think she has mastered that (and you), try out the canter and do the same thing.
Every green horse I've been in contact with is like this.
When you hit a road block, it's usually best to go back, practice all over again, and work on the road block another day and see if you can find out what little holes of training that would've caused that road block (makes sense?). I've had to do it several times with my gelding and now my mare, and it helps. Best of luck to you!!