Is my wife, to whom I am contractually wed, and who wishes to perform Salatul-Istikhara, entitled to annul the marriage and seek divorce if the result of the Istikhara is negative, despite a wedding date having been set?

Since the legitimate marriage contract has been concluded, the wife is now under the husband's protection, and the remaining arrangements, such as the wedding, are of no consequence. The wife does not have the right to leave her husband without his consent, unless she dislikes remaining with him for a valid reason, in which case she may request divorce (Talaq) or annulment (Khul'). Istikhara (prayer for guidance) was more appropriate before the marriage contract, because its time passes once the intention to act is firm. Furthermore, it is not permissible to seek divorce except for a valid reason. Pessimism and omens are forms of shirk (polytheism). Istikhara is a supplication in which the servant asks Allah to choose what is best for him, and if Allah responds, He will facilitate what is good and avert what is evil. What some people see in dreams after Istikhara has no reality, but a feeling of relief after it may be an indication to proceed with the matter.