I don't think you are being unreasonable. You were fair and judging by your work you will have no shortage of people looking to shoot with you. If she continues to push the issue I would agree with others here and say collect a refundable deposit and let her know that if she cancells again, she's going to loose it. This way she will know there is value for your time and you will know if she is serious about shooting with you.  -M