Yerushalmi Yevamot 15:7 ירושלמי יבמות ט״ו:ז׳

MISHNAH: If a woman went overseas with her husband and she returns and says “my husband died”, she can remarry and collect her ketubah, but her co-wife remains forbidden¹⁴⁰Since the testimony of a wife cannot be trusted in matters of her co-wife.. If she was the daughter of an Israel married to a Cohen¹⁴¹And she has no son on whose behalf she remains in the priestly clan and continues to eat heave., she should eat heave, the words of Rebbi Tarphon. Rebbi Aqiba says, in this way one does not remove her from sin unless she be forbidden to remarry¹⁴²Since perhaps her co-wife is ready to put herself in a perilous position in order to damage her co-wife. and forbidden to eat heave¹⁴³Since perhaps the testimony of her co-wife was true..

HALAKHAH: She is suspected to cause trouble to herself in order to cause trouble to her co-wife¹⁴⁴She is ready to forbid herself to her husband if it causes her co-wife to be equally forbidden.. Then she should not be trustworthy even for herself! Since she knows that her word does not count for the other woman, she will be truthful¹⁴⁵Cf. Halakhah 4, Note 94.. Then she should be trustworthy even for her co-wife! ¹⁴⁶Ms. A has an addition: . אָמַר רִבִּי הִילָא חֲזוֹר לְקִילקוּל הָרִאשׁוֹן חֲשׁוּדָה הִיא“Rebbi Ila said, go back to the first trouble; she is suspected …”. She is suspected to cause trouble to herself in order to cause trouble to her co-wife.