Is it permissible for the wife to refuse to give the key to her apartment to her husband's parents, and intentionally cut off the electricity in it to prevent them from sitting there, with her husband's consent, and is she considered to be oppressing them by doing so?

If a father grants a dwelling to his son and the son takes possession of it, then its ownership is complete for him, and no one else is permitted to reside in it without his permission. The wife has the right to independent housing. It would have been better to enable the husband's parents to reside in the apartment if they desired to do so, due to their rights, while allocating a room for the wife.

However, there is no blame upon the wife for preventing the husband's parents from residing [there] if this is with the husband's consent and the parents are not in need of the dwelling. Their supplication against her in this case is impermissible because it is an injustice, and it is a form of aggression that is likely to be rejected, for the Prophet, peace and blessings be upon him, said: "The supplication of a servant is answered as long as he does not supplicate for a sin or the severance of kinship ties, as long as he does not rush." And he said: "There is no Muslim on earth who supplicates to Allah with a supplication except that Allah grants it to him, or averts from him an evil equivalent to it, as long as he does not supplicate for a sin or the severance of kinship ties." This supplication involves sin and severance of kinship ties.