As the mishna discusses the requirement to observe local customs, the Gemara relates: The residents of Beit She’an were accustomed not to travel from Tyre to market day in Sidon on Shabbat eve. In deference to Shabbat, they adopted a stringency and would not interrupt their Shabbat preparations even for a short sea voyage. Their children came before Rabbi Yoḥanan to request that he repeal this custom. They said to him: Due to their wealth, it was possible for our fathers to earn a living without traveling to the market on Friday; however, it is not possible for us to do so. He said to them: Your fathers already accepted this virtuous custom upon themselves, and it remains in effect for you, as it is stated: “My son, hear your father’s rebuke and do not abandon your mother’s teaching” (Proverbs 1:8). In addition to adhering to one’s father’s rebuke, i.e., halakha, one is also required to preserve his mother’s teaching, i.e., ancestral customs.

In places that have different practices that are like two courts within one city, half rule in accordance with Beit Shammai and half rule in accordance with Beit Hillel, which is not considered a violation of "lo titgodedu" do not be divided into groups as it says in the first chapter of Tractate Yevamot. [If] a man from one community marries a woman from another community there is no doubt that the woman becomes subsumed under the husband in all his obligations since a man's wife is like himself for all matters and separates from her father's community. And this is an obvious matter and there is no doubt that there shouldn't be two people at one table who are able to eat different dough, that dough that is prohibited for one is permissible for the other… And the question is if a woman is widowed should she return to the practices of her father's home like before she was married and remain with her husband's practices like before she was widowed and it seems that if they have children she should follow the practices that the children follow but if she doesn't have children she should return to her father's home. This is learned from the Torah and Rabbis regarding the matter of a daughter of a Kohen who married a Yisrael who can no longer eat teruma and if she is widowed and has children she still can't eat teruma but if she has no children she can go back to [the rules of] her father's home.

MISHNA: In a place where the people were accustomed to perform labor on Passover eve until midday, one may do so on that day. In a place where the people were accustomed not to perform labor, one may not do so. The performance of labor on the eve of Passover is not prohibited by Torah law, but is dependent on local custom. If one travels from a place where people perform labor on Passover eve to a place where people do not perform labor, or from a place where people do not perform labor on Passover eve to a place where people perform labor, the Sages impose upon him the stringencies of both the place from which he left and the stringencies of the place to which he went. In both cases, he may not perform labor.

The Gemara asks: And does Rabbi Zeira not accept the principle that when a person travels from place to place, the Sages impose upon him the stringencies of the place from which he emerged and the stringencies of the place to which he went?Abaye said: That statement applies when one travels from one place in Babylonia to another place in Babylonia, or from one place in Eretz Yisrael to another place in Eretz Yisrael, or alternatively, when one descends from Eretz Yisrael to Babylonia. But when one ascends from Babylonia to Eretz Yisrael, this principle does not apply. Since we, the residents of Babylonia, are subordinate to them in terms of halakha, we act in accordance with their custom. Rav Ashi said: Even if you say that when one travels from Babylonia to Eretz Yisrael, he is required to act stringently in accordance with the custom of the place from which he emerged, that statement applies only in a case where his intent is to return. Rabbi Zeira was not one whose intent was to return. Therefore, he was not obligated to observe the Babylonian stringencies.

And so too those who come from outside the city to live there, they are like the dwellers of the city and are obligated to follow all their rules, and even regarding matters that were prohibited for them in their city because of the custom but the custom of the new city is to permit those things, those things are permitted if they don't intend to return.

A man takes a woman [into his household as his wife] and becomes her husband. She fails to please him because he finds something obnoxious about her, and he writes her a bill of divorcement, hands it to her, and sends her away from his house.

And one friend showed me that R' Ovayda Yosef wrote otherwise in Ohr Torah Iyar 5751, and this is what he says--customs that the husband is obligated to observe in accordance with his family tradition like Sephardim that received rulings from the Shulchan Arukh and aren't allowed to be lenient against his opinion even with annulment, it is appropriate for an Ashkenazi woman to follow her husband's customs and even when this is a leniency for her. But, stringencies that a husband took upon himself that if he wanted to he could renege on them with annulment, there is no obligation for the woman to follow these practices and he can't coerce her into this stringency that she doesn't want to observe when she has an opinion on which to rely. And therefore, if she wishes to continue to use T'nuva milk, she can and if the husband wants to be stringent he can but he can't require her to not bring T'nuva products into the house. And the same applies to Shemita fruits--if she relies on the Heter Mechira since many Torah giants are lenient regarding it, she can continue to be lenient and he can't force her to be strict and only use Badatz products.

There is what to challenge regarding the reasoning that a woman is like one who moves to her husband's home and doesn’t intend to return because it seems that this issue is subject to debate between R' Tam an Maharam of Rotenberg in Ketubot. According to R' Tam the woman's strength is greater than the man's and a husband can be forced to leave his hometown and to dwell in the place where the wife is from if the two places are equal and who says this isn't talking about two places with different customs and then you would find the man coming to live in the wife's town and he would have to follow the customs of that place and also once he's coming to her town, maybe he is going to live in her house. And I don't understand the reasoning of R' Moshe Feinstein that a woman's place is to be with her husband according to Torah Law because this is in fact true but it's also true that the husband's place is to be with the wife as it says "Therefore a man leaves his father and mother and clings to his wife and they become like one flesh" but this isn't specifically in his house or her…and when it says "he sends her out of his house" the Torah is just speaking in terms that are what usually occur.

See what is written in the responsa of the Tashbetz that a woman is subsumed under her husband's obligations because she is like him regarding all matters--this needs limits--because that phrase in the Gemara is used in the context of relatives and testimony and some say agency but not regarding obligations.

As far as a ruling- we should not reject common practice that the wife becomes free of her family's practices and follows her husband's practices if she wants, but she can rely on R' Ovadya Yosef and also in my humble opinion, things that are not between him and her and aren't difficult, she could continue practicing her family's customs and even if she accepts this upon herself anew after the marriage the husband can't undo it, but she should make this condition with her husband before they get married that she plans to continue practicing her family's customs.