It sounds like she may be MUCH greener than you thought??
I’ve noticed with my filly, she has displayed some undesirable behaviors (half-hearted rearing) during parts of the learning process where she doesn’t understand what’s being asked of her and is frustrated. This was EXTREMELY worrying to me at first, but those behaviors go away the instant she understands what is being asked and then she’s back to her dopey baby self.
From what you’ve described, I highly doubt this is entirely what’s been going on in this case. I definitely suspect there’s something pain related. But I wonder how much she truly “knows”? From the timeline of her life, I don’t think it’s much…
All of that being said, your safety is of utmost priority.