If the court ordered mediation you don't get to consent.
It should not matter to you what firm she is associated with, she maintained her relationship with you. She is your lawyer, and the firm she is at does not affect her responsibilities or behavior to you. Doctors and lawyers cannot sign a "noncompete" because it would not be fair to the clients who want to stay with their lawyer, so this is common.
You will owe her for whatever hours she put in, regardless of what you decide to do in the future as long as she has not committed malpractice. When you hire a lawyer she has certain duties. However, the TACTICS (motions etc) are her choice - you don't get to micromanage the lawyer you hire. You DO have the right to see any offers and decide whether to accept them. She did not abandon the property settlement just because she finishes it at the new firm. Nothing you mention rises to the level of malpractice. And if you think lawyers stick together, try to sue a doctor.
That being said, you are free to end your relationship with her and get another if you want - but NOT to refuse to pay for what she has done. That's probably in your contract.
There is a code that requires ethical behavior. We usually agree because it is the best answer, not because we like each other.
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First, the NJ courts web page has a form you can download and use to file an ethics grievance. It also has a form you can download to file a fee grievance. Ethics and fee disputes are handled by separate committees. Second, if you truly think your client committed malpractice, then invest in a consultation with a legal malpractice attorney. Expect to pay a consultation fee. Lastly, drop the attitude. The mere fact that there are plenty of lawyers who are willing to sue other lawyers should tell you we don't "all" stick together.
A couple of general points: Mediation is usually court-ordered. There is no consent involved. There is nothing unethical or which constitutes malpractice if a lawyer shuts her practice and joins another firm. If your retainer agreement requires you to pay her for her time and expenses, then that is what you owe. Good luck.
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