The walking backwards and keeping head down make me think of AAI. I don't know about the other symptoms....but, with neuro often there is a mix of conditions...
https://www.acvs.org/small-animal/at...al-instability
Until you know what this is, I suggest you keep her activity level to a minimum.
I sent an email to a specialist I know but don't know when I might hear back....will let you know if I hear something.