I think she's too young. That's my opinion. Your riding her at two? Her mind isn't fully developed yet. How much ground driving and training have you done before getting on her back? I'd be real careful going to fast with her training because things like this do develop. I think before you go forward with this issue you need to back up and lunge her more tacked up. Can or have you tried to ground drive her tacked up? It sounds like she isn't used to the weight and gets confused and a bit scared and her reaction is to get whatever is scaring her off or away from her.
I would definitely go back to lunging in the round pen. When you get her moving forward without trouble on the ground, have your assistant lunge with you on her back. Now, don't be too concerned with which way she goes or steering her. Try to let her move where she wants as long as she is moving forward. Go slow, but don't continue to ride her until you go back to the round pen.
My filly is two and a half. I have only started to just sit on her. I don't make her move but let her do it on her own. If she stops its because she's just not to sure about that extra weight up there.
As far as she's bored, hand walk her. Take her around the property and let her see different things. I honestly think she needs another year to mature psychologically and physically but that's my opinion. Have you had a vet out to check if her knees are closed? Posted via Mobile Device