Praise be to Allah.
Allaah has enjoined the Muslims to be sincere to one another, and He has enjoined the one who has been advised sincerely to respond to the command of Allaah, may He be exalted, and to refrain from the evil actions that he is committing. Hence you must advise:
1 – Your brother’s wife, and tell her to stop doing things that Allaah has forbidden such as uncovering any part of her body in front of her husband’s brothers, speaking softly to them and mistreating you.
2 – Your brother himself, and tell him to stop his wife from mixing with non-mahram men and to stop her from mistreating his sisters. And he should pay attention to the evils that she is causing in the family, such as creating division between his brothers and their wives.
3 –Your parents should take a stance concerning the actions of their son’s wife.
4 – The husband’s brothers should not sit with their brother’s wife or listen to what she says; they should beware lest she become a cause of division among the family, and division between them and their wives.
She has to know and respect the sacred limits set by Allaah, and her husband – likewise – must realize that his wife is part of his flock that Islam enjoins him to take care of. He should realize that he will be responsible on the Day of Resurrection for her and her actions.
Among the things that Islam has enjoined upon her are the following:
1 – She should preserve her modesty and chastity, and lower her gaze and avoid looking at that which Allaah has forbidden.
Allaah says (interpretation of the meaning):
“And tell the believing women to lower their gaze (from looking at forbidden things), and protect their private parts (from illegal sexual acts) and not to show off their adornment except only that which is apparent (like both eyes for necessity to see the way, or outer palms of hands or one eye or dress like veil, gloves, headcover, apron), and to draw their veils all over Juyoobihinna (i.e. their bodies, faces, necks and bosoms) and not to reveal their adornment except to their husbands, or their fathers, or their husband’s fathers, or their sons, or their husband’s sons, or their brothers or their brother’s sons, or their sister’s sons, or their (Muslim) women (i.e. their sisters in Islam), or the (female) slaves whom their right hands possess, or old male servants who lack vigour, or small children who have no sense of feminine sex. And let them not stamp their feet so as to reveal what they hide of their adornment. And all of you beg Allaah to forgive you all, O believers, that you may be successful”
Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him) said:
Many scholars are of the view that it is not permissible for a woman to look at non-mahram men with desire.
Majmoo’ al-Fataawa (15/396).
2 – She should observe complete hijab before non-mahram men, and she should realize that her husband’s brothers are also non-mahrams. Indeed, she should be more careful about her clothing, adornment and speech before them than before others. The verse from Soorat al-Noor quoted above makes it clear that it is not permissible for her to show her adornments in front of them.
It was narrated from ‘Uqbah ibn ‘Aamir (may Allaah be pleased with him) that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Beware of entering upon women.” An Ansaari man said: O Messenger of Allaah, what about the in-law? He said: “The in-law is death.”
Narrated by al-Bukhaari (4934) and Muslim (2172).
See Imam al-Nawawi’s comment on this hadeeth in the answer to question no. 12837.
3 – She should adhere to the Islamic rulings on speaking to non-mahram men and on walking, so there should be no softness or allure in her speech or actions. Allaah says (interpretation of the meaning):
“then be not soft in speech, lest he in whose heart is a disease (of hypocrisy, or evil desire for adultery) should be moved with desire, but speak in an honourable manner”
4 – Avoiding wearing perfume that can be smelled by non-mahrams.
It was narrated that Abu Moosa al-Ash’ari (may Allaah be pleased with him) said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Any woman who puts on perfume and passes by people so that they may smell her fragrance is a zaaniyah (adulteress).”
Narrated by al-Tirmidhi (2786), Abu Dawood (4173) and al-Nasaa’i (5126; classed as hasan by al-Albaani in Saheeh Abi Dawood.
5 – Refraining from being alone with her husband’s brothers and mixing with them.
It was narrated that Ibn ‘Abbaas (may Allaah be pleased with him) said: I heard the Prophet (peace and blessings of Allaah be upon him) say: “No man should be alone with a woman unless she has a mahram with her.” Narrated by al-Bukhaari (1763) and Muslim 91341).
Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allaah have mercy on him) said:
Is it permissible for a woman to sit with her husband’s relatives if she is wearing Sunnah hijab?
It is permissible for a woman to sit with her husband’s brothers or her cousins and so on if she is wearing proper shar’i hijab, which means covering the face and the rest of her body, because she is ‘awrah and a fitnah, if the sitting mentioned does not involve anything dubious. As for gatherings in which there is anything dubious, that is not permissible. The same applies to sitting with them and listening to music or entertainment and the like.
It is not permissible for her to be alone with any one of them or with anyone else who is not a mahram for her, because the Prophet (peace and blessings of Allaah be upon him) said: “No man should be alone with a woman unless she has a mahram with her.” Saheeh – agreed upon. And he (peace and blessings of Allaah be upon him) said: “No man is alone with a woman but the shaytaan is the third one present.” Narrated by Imam Ahmad with a saheeh isnaad from the hadeeth of ‘Umar ibn al-Khattaab (may Allaah be pleased with him). End quote.
Fataawa al-Mar’ah al-Muslimah (1/422, 423).
The husband should heed these commands and prohibitions, and he should realize that he is responsible for his wife, so he must advise her and direct her to that which is good. Guiding her is preferable, in our view, to letting her go or divorcing her.
The parents should also take a firm stance regarding this issue. The mother should stand up for what is right, and not let her emotions take precedence over sharee’ah and common sense. She should understand that if her son’s wife carries on in this manner, this will destroy her son’s family and the negative effects of that are obvious as mentioned in the question.
The wife’s brothers should also fear Allaah with regard to themselves and be content with the halaal things that Allaah has blessed them with. They should advise their brother and guide him and his wife lest their relationships with their own wives be spoiled. They should also lower their gaze and avoid mixed gatherings.
We ask Allaah to set the affairs of all the Muslims straight.
And Allaah knows best.