Is it permissible for a female student to dispose of the amount designated for dental treatment, which she receives from the company, before completing the treatment, due to her conviction that the doctor is incompetent, and that if she did not do so, the company would take the excess amounts, especially since the company donates the excess amounts to Israel?

Funds granted by the government to students and others must be used in accordance with the conditions of the granting entity. If the funds are for medical treatment, then it is not permissible to spend them on anything else, and any remaining amount after treatment must be returned to the granting entity.

If it is highly probable that the money will be lost or spent in vain if returned, then it must be spent on the welfare of Muslims, and not taken for oneself.

As for the doctor's right: If the agreement was for a specific treatment at a known fee, and you paid part of the fee while some treatment remains, then you are obliged to continue with her as long as she is capable of treating you and you do not suffer harm. If harm occurs, it is an excuse to terminate the contract, and she is entitled to payment for what she has done. If this is not the case, then there is no harm in not continuing, but it is preferable to fulfill the promise unless there is an excuse, such as the availability of a more skilled doctor.