A woman is expected to show her husband's parents the respect and kindness that are due from a dutiful daughter while her husband must treat his parents with kindness at all times and under all circumstances. If we say that a woman is supposed to act in unison with her husband, then the least she may do is to treat them with the respect due to a parent. Having said that, I should add that what we are talking about here is a genuine attitude manifested in behavior. Behavior, however, is different from service.
According to Islam, a woman is not required to serve her husband's parents. He himself is required to look after his parents and try as hard as possible to ensure their comfort according to his means. This means that if a woman decides to serve her husband's parents, in deference to them or out of love for her husband, she does so voluntarily. Her attitude should be met with gratitude by her husband and his parents and her kindness should be reciprocated. But she violates no Islamic law or principle if she decides not to serve them. Her husband may not force or pressure her into serving them, whether they share the same house or live separately.
When we understand these limitations, the relationship between parents and their daughter-in-law acquires a different outlook. When someone does you a favor voluntarily and you do not show your appreciation, they are bound to feel hurt. The least to be expected is that they do not readily continue to do you favors. When the kindness is returned or at least appreciated, they are encouraged to continue this generous attitude. If, on the other hand, a person is made to feel that a voluntary favor is expected as a duty when no religious or moral authority imposes it, then an attitude of rebellion begins to make itself felt. This may be the key to the whole problem about which you ask.
What I detect from your letter is that your wife has been made to serve your parents with whom you live, and she was made to understand that it was her duty. I am not sure what her initial reaction was, but she might have accepted it, perhaps reluctantly, at first. She might have felt later that what was required of her was actually too much, or constituted a burden on her. You did not give me any idea about your family situation, but it is not difficult to think of many situations when serving parents-in-law can be a real burden.
Suppose a woman has young children of her own and has to look after them. Nowadays, young children are too demanding and the burden they present is quite a heavy one. Our modern times are different. In the past, a couple lived with their extended family and a woman received the help she needed with bringing up her young children from the other women in the family.
If a woman has to serve her parents-in-law, she may find that she is required to work long hours without getting enough rest. There is also the possibility of conflict between your wife and parents. This may come about from feeling that her service is not appreciated. As time goes on, this leads to strained relations and, probably, an outburst of temper from either side. It is very difficult to remedy the situation when it reaches this stage.
In circumstances like these, a woman is within her right to ask her husband to move out of the family house. She wants to look after her immediate family and avoid frequent conflicts with her husband’s parents. Obviously the advantage she sees in living alone is significant since she will be under no pressure and can organize her family to her satisfaction.
It is normal in certain societies, that when the relationship within the family reaches this stage, the husband's parents may ask or suggest that he divorce his wife. What should a husband do in such a case? If he acts on his parent's wishes, he would do his wife and himself a great wrong. He must not forget that he is duty bound to look after his wife and give her a comfortable life according to his means. He therefore has the dual responsibility of looking after his wife as well as his parents. If he cannot fulfill both responsibilities when he and his wife are sharing the same house with his parents, it may be highly advisable for him to move out. And if this prompts his parents to ask him to divorce her, he must not do so provided his wife fulfills her duties toward him, their children and his parents. Once again, she is only obliged to treat them with respect and kindness. Maybe when they move out, she would be better able to fulfill that duty and make it felt by them. This is a typical Oriental family problem. Islam has provided an easy solution for it, requiring everyone in the family to understand their duties and rights.
Some readers may feel that I am taking the wife’s side. I wish to make it clear that I am not. I realize that there are women who are selfish and create problems within the family. A woman of this type should not be treated in the same way as a kind, dutiful woman who knows her rights and duties.
Based on this, a woman is within her right to ask her husband to provide her and their family with a separate home. She is also within her right if she decides not to serve her parents-in-law. It is wrong for parents to ask their son to divorce his wife because she does not serve them. Islam does not condone this provided she observes the duties enjoined upon her. Her husband must not act on his parents' wishes to divorce her because this would be a grave wrong.