Praise be to Allah.
The child – male or female – is obliged to spend on his (or her) parents if they are poor and he is rich. The obligation of spending on them is indicated by the Qur’aan, Sunnah and scholarly consensus (ijmaa’).
Allaah says (interpretation of the meaning):
“And your Lord has decreed that you worship none but Him. And that you be dutiful to your parents”
Being dutiful includes spending on them if they are in need.
It was narrated from ‘Aa’ishah (may Allaah be pleased with her) that the Prophet (peace and blessings of Allaah be upon him) said: “Among the best of that which a man consumes is what he earns (by his own efforts), and his son is part of that which he earns.” Narrated by Abu Dawood (3528) and classed as saheeh by al-Albaani in Saheeh Abi Dawood.
Ibn al-Mundhir said: The scholars are unanimously agreed that spending on poor parents who have no income or wealth is an obligation on the child’s wealth. End quote.
A man asked the Prophet (peace and blessings of Allaah be upon him): Which of the people is most deserving of my good companionship? He said: “Your mother.” He said: Then who? He said: “Then your mother.” He said: Then who? He said: “Then your mother.” He said: Then who? He said: “Then your father.” Narrated by al-Bukhaari (5971) and Muslim (2548).
It is obligatory to spend on grandfathers and grandmothers on the father’s side and on the mother’s. This is the view of the majority of scholars (including the three imams, Abu Haneefah, al-Shaafa’i and Ahmad), because the grandfather is also called a “father”. Allaah says (interpretation of the meaning): “it is the religion of your father Ibraaheem (Abraham)” [al-Hajj 22:78].
And Allaah says (interpretation of the meaning): “And marry not women whom your fathers married” [al-Nisa’ 4:22]. Here “fathers” includes the father and the grandfather on both the father’s and mother’s side.
And Allaah says (interpretation of the meaning): “For parents, a sixth share of inheritance to each if the deceased left children” [al-Nisa’ 4:11]. Here “parents” includes both the grandfather and the grandmother.
The grandmother is also called a mother. Allaah says (interpretation of the meaning): “Forbidden to you (for marriage) are: your mothers” [al-Nisa’ 4:23]. This includes the mother and grandmother, according to scholarly consensus.
As the grandfather is called a “father” and the grandmother is called a “mother”, they are included in the evidence which indicates that it is obligatory to be dutiful towards one’s parents and spend on them.
See: al-Mughni (11/372).
Ibn ‘Uthaymeen said in al-Sharh al-Mumti’ (13/498-499), in the chapter on spending on relatives:
The ascendants are those from whom you stem of fathers and mothers.
The descendants are those who stem from you of sons and daughters.
Then he said:
It should be noted that this topic is like the topic of prohibition of marriage, and there is no difference between the father’s side and the mother’s side. The ascendants and descendants are the same, whether they are relatives on the mother’s side or relatives on the father’s side. You are obliged to spend on them, but that is subject to conditions. End quote.
In order for it to be obligatory to spend on fathers and grandfathers, they should be poor and the child should be rich, because the Prophet (peace and blessings of Allaah be upon him) said: “Start with yourself and give charity to yourself. If there is anything left over, then (give) to your family. If there is anything left over from your family, then (give) to your relatives.” Narrated by Muslim (997).
Shaykh Ibn Jibreen (may Allaah preserve him) said: If the parents are poor and the daughter has wealth surplus to her needs, then she is obliged to spend on her parents according to their needs, without it detracting from her needs. End quote.
Based on this, the woman is obliged to spend on her parents if she is rich and they are poor.