Mishnayos Yevamos Perek 15 Mishnah 6

In the case of a woman who went, she and her husband, overseas, and she comes and says: My husband died, she may marry, and she takes her marriage contract based on her own testimony. And it remains prohibited for her rival wife to remarry, as a woman cannot testify on behalf of her rival wife. If the rival wife was an Israelite woman married to a priest, she may continue to partake of teruma, as she is not permitted to remarry, and therefore the presumption that the husband is still alive is maintained in relation to her. This is the statement of Rabbi Tarfon. Rabbi Akiva says: This is not the way to spare someone from transgression. According to the opinion of Rabbi Tarfon, there is a concern that she might be eating teruma unlawfully. There is no remedy for this situation unless it is prohibited for the rival wife to marry, as she cannot rely on the testimony of her rival wife, and it is also prohibited for her to partake of teruma, lest the other woman was speaking the truth. In other words, the halakha is stringent on both counts.

הָאִשָּׁה שֶׁהָלְכָה הִיא וּבַעְלָהּ לִמְדִינַת הַיָּם, וּבָאָה וְאָמְרָה מֵת בַּעְלִי, תִּנָּשֵׂא וְתִטֹּל כְּתֻבָּתָהּ, וְצָרָתָהּ אֲסוּרָה. הָיְתָה בַת יִשְׂרָאֵל לְכֹהֵן, תֹּאכַל בַּתְּרוּמָה, דִּבְרֵי רַבִּי טַרְפוֹן. רַבִּי עֲקִיבָא אוֹמֵר, אֵין זוֹ דֶרֶךְ מוֹצִיאַתָּה מִידֵי עֲבֵרָה, עַד שֶׁתְּהֵא אֲסוּרָה לִנָּשֵׂא, וַאֲסוּרָה מִלֶּאֱכֹל בַּתְּרוּמָה: