Hi, welcome to the ehealth forum and I am glad to help you. You seem to be concerned by the sleep paralysis lasting for a week in the daughter of your sister in law.
Sleep paralysis usually is part of Narcolepsy, a neurological condition in which person has uncontrollable naps but isolated sleep paralysis is also known to occur. Sleep paralysis consists of a period of inability to perform voluntary movements either at sleep onset (called hypnagogic or predormital form) or upon awakening (called hypnopompic or postdormital form).Sleep paralysis occurs when the brain awakes from a REM state, but the body paralysis persists. This leaves the person fully conscious, but unable to move. The paralysis can last from several seconds to several minutes "after which the individual may experience panic symptoms and the realization that the distorted perceptions were false". Sleep paralysis isn't harmful, but those experiencing sleep paralysis are frequently fearful since they do not know what is happening to them. Typically ended by stimuli such as sound or touch, within a matter of seconds to minutes after a bout of sleep paralysis, the person is able to move again. Medications such as Sodium oxybate (Xyrem) may be prescribed as a cure for sleep paralysis in severe cases, but the best treatment for sleep paralysis is to reduce stress and get the proper amount of sleep by following a good sleep hygiene. But in your case you have mentioned that the state of sleep paralysis lasts for one continuous week which has not been reported in the medical literature. The duration of sleep paralysis is from few seconds to minutes as per medical literature. The cause of sleep paralysis is not known as to why this occurs and is sometimes known to be familial also. In the case that you have mentioned it's important to consider alternative diagnosis. There may be an organic lesion in the brain that may be causing the paralysis which needs to be investigated in consultation with a neurologist taking a detailed history, thorough examination to look for focal signs and MRI brain etc.
Hope this helps. Take care.
Note: This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.