Reading Nedarim 90.
(a) I don't understand how can a woman go and say that she is inpure. Is it in the case of rape? otherwise isn't she punished for being unfaithfull? Is this the wife of a Priest or also the wife of an Israel.
(b) What does it mean: May I be removed from the Jews in order to get back a Ketubah?
Thanks for your answer
Mexico City. Mexico
(a) The Mishnah there is discussing a case of the wife of a Kohen. When, G-d forbid, the wife of a Kohen is raped, the Kohen and his wife are not permitted to remain married. Since it was not her fault, though, she is entitled to receive her Kesuvah. The wife of a Yisrael may remain married to her husband even after someone rapes her, and thus the Mishnah is not discussing such a case. A woman who is purposely unfaithful to her husband does not receive a Kesuvah.
(b) The third case in the Mishnah is a woman who makes a Neder prohibiting herself from marital relations with any Jew. Since she makes such a Neder, it is clear and obvious that the act of marital relations is very painful to her, and thus since she finds marriage so difficult, her husband must divorce her and give her the Kesuvah.
I hope these answers were helpful.