You can refuse to pay but she may sue you for any money you owe her. It is not clear to me what you are being billed for: the work already performed or the work she was going to perform. If she specially ordered a crown or any other device for you, you may have to pay for that as well.
You owe her for the value of the work she did. If you agreed to pay her for certain work, and you fired her for no good reason while she was doing the work, you owe her damages for breaching your contract with her; perhaps the entire contract price.
This is a summary based on incomplete facts. You should not rely on it as legal advise. No attorney-client relationship is intended to be formed. You may call me 772-562-4570; email me firstname.lastname@example.org, or visit my website http://www.millerlawoffices.us
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