Do you have any idea why Rashi on 39b changes an identical, consecutive remark from Hebrew to Aramaic in two of his commentaries? He first says (DH Bas Rav Chisda), "Ishto Shel Rava" (in Hebrew) and then he says (DH Bas Aba Sura'ah), "Devis'hu d'Rav Papa" (in Aramaic)?
We sent your question to Rav Yakov D. Homnick who answered as follows:
When Rashi switches languages from the text, Aramaic to Hebrew or vice versa, it's to put some distance between the subject and his comment. Here he is trying to alert us to both the advantage that Bat Rav Chisda has as a source and to her shortcoming. Presumably the Gemara uses two sources only if each has a point of superiority over the other. Bat Rav Chisda has the advantage, as the daughter of an Amora, of having absorbed the culture of Halachic objectivity even before her marriage. See also Rashi Shabbat 95a about "Ishah Chachamah".
Her disadvantage lies in the fact that her marriage to Rava was her second, as per Bava Batra 12b, so she might have been motivated to exaggerate the unpleasantness of her initial intimate experience in relating it to a later partner.
Both of these aspects are highlighted by Rashi's abstraction of her identity as an individual apart from the tempo of the text.
See also Har Tzvi, Beis Pinchas, and Mishmar Ha'levi