וַתָּ֤מָת דְּבֹרָה֙ מֵינֶ֣קֶת רִבְקָ֔ה וַתִּקָּבֵ֛ר מִתַּ֥חַת לְבֵֽית־אֵ֖ל תַּ֣חַת הָֽאַלּ֑וֹן וַיִּקְרָ֥א שְׁמ֖וֹ אַלּ֥וֹן בָּכֽוּת׃
And Devorah, the nurse of Rivkah, died, and she was buried below Beis-El under the oak; and he called its name Allon-bachus.
Torah Temimah points to Bereishis Rabbah 81:5.
Sefaria · Bereishis Rabbah 81:5
ותמת דבורה מינקת רבקה — למה נזכרה כאן? ללמדך שכל זמן שדבורה קיימת היתה רבקה קיימת.
“And Devorah the nurse of Rivkah died” — why is she mentioned here? To teach you that as long as Devorah was alive, Rivkah was alive.
The Midrash connects the death of the nurse with the unmentioned death of Rivkah.
Derash on the timing of the death (Bereishis Rabbah).
The death of Devorah is recorded here to indicate the concurrent death of Rivkah, which is not stated explicitly.