You have no legal grounds to not pay the agreed-upon fee: that she is "very snappy and pushy" is certainly reason to not use her again or not recommend her but is not a breach of contract. In the absence of some breach by her, you are bound to pay her the fee you agreed to pay. You can try to renegotiate, and maybe she will voluntarily accept a reduction, but she does not have to; she can hold you to the full fee.