You probably would fail unless you believe you can show that she is doing this for improper or malicious reasons, and not because of a good-faith belief on her part--even a mistaken belief; the issue is not whether she is correct, but whether she honestly believes in what she is doing--that your charge was excessive, or improper, or that you did not due the work you'd promised to a commerially acceptable level of quality. Only if her motives are bad might you win a harassment suit.