Mishnayos Niddah Perek 4 Mishnah 2

With regard to Sadducee girls, when they were accustomed to follow in the ways of their Sadducee ancestors their status is like that of Samaritan women, whose halakha was discussed in the previous mishna. If the Sadducee women abandoned the customs of their ancestors in order to follow in the ways of the Jewish people their status is like that of a Jewish woman. Rabbi Yosei says: Their status is always like that of a Jewish woman, until they will abandon the ways of the Jewish people in order to follow in the ways of their Sadducee ancestors.

בְּנוֹת צְדוֹקִין, בִּזְמַן שֶׁנָּהֲגוּ לָלֶכֶת בְּדַרְכֵי אֲבוֹתֵיהֶן, הֲרֵי הֵן כְּכוּתִיּוֹת. פֵּרְשׁוּ לָלֶכֶת בְּדַרְכֵי יִשְׂרָאֵל, הֲרֵי הֵן כְּיִשְׂרְאֵלִית. רַבִּי יוֹסֵי אוֹמֵר, לְעוֹלָם הֵן כְּיִשְׂרָאֵל, עַד שֶׁיִּפְרְשׁוּ לָלֶכֶת בְּדַרְכֵי אֲבוֹתֵיהֶן: