She is sick and does not understand anything and is not aware of her surroundings. Does she have to feed the poor (in lieu of fasting)?
Question

                I have a sister who has been sick for three years, and she did not fast last year and the year before. Her problem is atrophy in the brain, and there is no hope of recovery. She does not speak or understand anything and she is not aware of her surroundings, and she does not know anything other than our names, her name and her daughter’s name. She has no control over her actions and she is virtually insane. She is confined to her bed and does not pray because she is not aware of anything. In her case, what is the Islamic ruling on her not fasting? If she has to feed the poor, how much is that in riyals?.
Praise be to Allah.In order for fasting to be 
    obligatory, it is stipulated that a person be of sound mind, because the 
    Prophet  (peace and blessings of Allaah be upon him) said: “The Pen has 
    been lifted from three: from the insane person until he comes back to his 
    senses, from the sleeper until he wakes up and from the minor until he 
    reaches puberty.” Narrated by Abu Dawood (4399); classed as saheeh by 
    al-Albaani in Saheeh Abi Dawood. 
As your sister has reached 
    this stage or being unaware and unable to distinguish anything, she is not 
    obliged to fast, and she does not have to make up missed fasts or feed the 
    poor instead. 
Prayer is like fasting; she 
    is not obliged to pray either. 
Shaykh Ibn ‘Uthaymeen (may 
    Allaah have mercy on him) said in al-Sharh al-Mumti’ (6/202): 
Anyone who is not of sound 
    mind is not accountable, and he does not have to do any of the duties 
    enjoined by Islam, such as praying, fasting, feeding the poor etc, i.e., he 
    does not have to do anything at all. Based on this the one who is 
    feeble-minded does not have to fast or feed the poor, because he has lost 
    the thing that qualified him to do that, namely his reason. End quote.