Gemara

The reason for Kesuvah is so it will not be light in a man's eyes to divorce his wife.

54b (R. Eibo): (Tosfos and other) stipulations of the Kesuvah are like the Kesuvah. This is relevant to ... a woman who transgresses Das (causes her husband to transgress Torah law, or does not behave like modest Bnos Yisrael).

72a (Mishnah): A woman is divorced without a Kesuvah for Overes Al Das. Das Yehudis forbids going out with her head uncovered, spinning in the market, or talking with every man.

101a (Beraisa): When Chachamim said 'she leaves without a Kesuvah', such as Overes Al Das (Moshe or Yehudis) and accompanying cases, she does not receive Tosefes, all the more so not 100 or 200.

Gitin 90a: If a man does not protest when he sees his wife go out with uncovered hair, weave in public with her elbows exposed, or bathe where men bathe, he is a Rasha. It is a Mitzvah to divorce such a woman - "He found in her immorality...he sent her from his house, and she married a different man."

Her ex-husband is "different" from her new husband. The former expelled evil from his house. The latter brings evil into his house, and he is worthy to be punished for this. If he merits, he will also divorce her. If not, he will die in her lifetime - "If the next husband... will divorce her...or die."

Yevamos 63b (Rava): It is a Mitzvah to divorce an evil wife - "Divorce the scoffer; expel quarrels and disgrace."

Sotah 25a - Question: May one remain married to a wife who is Overes Al Das?

Perhaps he may decide whether or not he minds. Or, since most men object to immorality, he may not choose!

Answer (Mishnah): Beis Din can warn the wife of a man who became deaf, or insane, or was imprisoned.

If her husband may remained married to her, Beis Din would not warn her, lest she become forbidden, and he would have wanted to keep her!

Rejection: Really, he may remain married to her, but we assume that he would not want to remain married to a wife who is Overes Al Das.

Rishonim

The Rif and Rosh (Gitin 51a and 9:15) bring the Gemara in Gitin, and the Mitzvah to divorce an evil wife.

Rif (Kesuvos 32b): When she was warned, she forfeits her Kesuvah, not only 100 or 200. She does take existing remnants (of her dowry).

Rosh (Kesuvos 11:25): Any woman who was permitted when she married, but caused that she must be divorced (e.g. through Zenus), does not receive Ikar Kesuvah or Tosefes. She does take existing remnants of her Nichsei Melug and Tzon Barzel.

Ran (Kesuvos 22a DH veli'Chsuvas): Perhaps Overes Al Das loses the dowry she brought in that is not intact. However, she gets back what is intact. Even one who was Mezanah does not lose this, for her property was not Mezanah (Kesuvos 101b)!

Rosh (7:9): A woman is divorced without a Kesuvah for transgressing Das Yehudis. The Gemara (Sotah 25a) did not resolve whether or not her husband is allowed to keep her. We do not force him, but it is a Mitzvah to divorce her.

Ran (DH b'Toveh): The Rashba says that presumably, the conclusion is (some texts - it is possible) that he may keep her if he wants. The Gemara (Sotah 25a) asked if one may keep an Overes Al Das, then it asked whether a husband can pardon his warning (against seclusion). It answered that he can, i.e. and all the more so one who never warned her may keep her!

Kesef Mishneh (Hilchos Ishus 24:16): We learn from Yevamos 24b. It says that Beis Din forces one to divorce his wife only if there are witnesses of Zenus.

Rambam (Hilchos Ishus 24:10): If a wife was Overes Al Das Yehudis, she does not get Ikar or Tosefes Kesuvah or any stipulations of the Kesuvah. She gets what remains of her dowry and leaves. Her husband need not compensate for what decreased in value or was lost.

Rambam (16): If a woman transgressed Das Moshe or Yehudis, or did something awful (suggesting Zenus), we do not force her husband to divorce her. It is his choice. Even if he does not divorce her, she has no Kesuvah. Chachamim enacted Kesuvah so it will not be light in a man's eyes to divorce his wife. Chachamim were concerned only for a Tzenu'ah Bas Yisrael.

Chelkas Mechokek (EH 115:18): If he kept her and she returned to be Tzenu'ah, he must write for her a new Kesuvah. Her old Kesuvah was pardoned when she transgressed the warning.

Beis Shmuel (19): The new Kesuvah is for 100.

Poskim

Shulchan Aruch (EH 115:1): If a wife was Overes Al Das Yehudis, she leaves without a Kesuvah.

Shulchan Aruch (4): Das Yehudis is the modest conduct of Bnos Yisrael. One who does any of the following transgresses Das Yehudis... She shows her arms to men while spinning (Rema - and does so regularly).

Beis Yosef (DH v'Chosav ha'Rashba): A case occurred in which a woman was arguing with her husband in the market, and exposed her hair and her arms were exposed. Some Chachamim judged her to be Overes Al Das for this. The Rashba disagreed, for Overes Al Das Moshe and Yehudis are not for one occurrence, rather, for one who regularly does so. I don't know why he didn't say that she is not Overes Al Das because she was not warned.

Darchei Moshe (5): It seems that she was warned.

Chelkas Mechokek (11): Why did the Rema add 'she does so regularly'? Without warning, in any case she is not Overes Al Das. If she was warned, she is Overes even for one time! Chachamim did not give a Shi'ur of how many times she must transgress. There is an error in Teshuvas ha'Rashba.

Gra (12): The Terumas ha'Deshen (242) says that if a woman transgresses regularly, this is great immorality and she need not be warned.

Beis Shmuel (11): In the episode, she exposed her arms due to anger. Therefore, the Rashba said that she is Overes only if she does so regularly. When there is no 'excuse' for indecent behavior, the Rashba agrees that she is Overes even for one time.

Beis Yosef (DH Chasuv bi'Teshuvas): The (Rashba, Teshuvos attributed to the) Ramban (102) says that one who curses her husband without reason leaves without a Kesuvah. I do not know his source. Perhaps he learns a Kal va'Chomer from cursing his father in front of him. This can be challenged. This is worse than cursing him, because Kivud Av is very severe! If it is true, one of the Poskim should have mentioned it. If he hits her regularly, he is not believed to say that she is uncouth and instigates by cursing him.

Shulchan Aruch (ibid.): In all of these cases, if there are witnesses that she was warned and transgressed, she leaves without a Kesuvah. If there are no witnesses (and she denies it), she swears like she says. If her husband wants to keep her we do not force him to divorce her. In any case it is a Mitzvah to divorce her.

Beis Yosef (DH Chasuv bi'Terumas): The Terumas ha'Deshen (242) says that a woman who is regularly secluded with Nochrim is Overes Al Das. Perhaps she need not be warned.

Chelkas Mechokek (18): The Ran cites the Rashba to say that he may keep her. This implies that it is not a Mitzvah to divorce her. It seems that the Rambam agrees. Gitin 90a says that it is a Mitzvah to divorce her. It discusses excessively lewd women.

Rema: She cannot stop him from divorcing her. R. Gershom's Cherem does not apply. If she threatened her husband that she will hire Nochrim to kill him if he does anything to her, or she regularly is secluded with Nochrim, this is Overes Al Das.

Beis Shmuel (20): Seclusion even once after warning is Overes Al Das Moshe. However, if it was for the sake of business, it is only if she does so regularly.

Shulchan Aruch (5): All of these do not receive Ikar Kesuvah, stipulations of the Kesuvah or Tosefes. She gets what remains of the Nichsei Melug and Nichsei Tzon Barzel. She cannot make her husband pay for what was consumed, stolen or lost.

Shulchan Aruch (119:4): If a woman has an evil mindset or is not Tzenu'ah like proper Bnos Yisrael, it is a Mitzvah to divorce her.