Is feeling distressed and uneasy about the prospective marital home, and requesting to change it despite the fiancé's family's insistence on keeping it, considered an act of ingratitude (baṭar) or forbidden (ḥarām), and what is the correct action in this situation?

The summary of the answer:

The Prophet, peace and blessings be upon him, forbade tatayyur (superstitious belief in omens). Some scholars interpreted the ill-omen of a woman as her being barren, the ill-omen of a horse as its not being suitable for raiding, and the ill-omen of a house as having a bad neighbor. Malik did not intend to attribute ill-omen to the house itself, but rather it is due to customary occurrences, and a person should leave it to protect their belief from being attached to falsehood. This is similar to the command to flee from a leper to block the means (to harm). So, if this happens to a person concerning a house, they should hasten to move out of it, lest they fall into believing in the validity of tirah (omen-taking) and pessimism.