Is it time to leave this barn?

That is a ridiculous amount of money for what you are getting. It seems to me she knew exactly what she was doing and is hoping you will quietly keep stumping up the cash. I would firmly state that this was not your understanding of the situation and you are not prepared to continue with this, also that you will pay for the lessons you had last month but no more. You can then either go back to as you were or move yards. To say it was the only way to start doing more advanced jumping is absolute rubbish too. I would move for sure.