Deer can absolutely stand on two legs, and even stumble around a bit. Here is an example, looks like it’s in search of food:
https://m.youtube.com/watch?v=MmBlC24jonM&pp=
Anyhow, I do agree it’s very improbable, but the story is certainly possible, especially if you ignore the likely hyperbole about “brains everywhere”.
Well that horse is majestic af. I am going to go ahead and assume she enjoys performing the trick, otherwise I wish her luck in crushing her captors.