The medrash tells us on the night Rachel was supposed to be married to Yaakov Avenu, her father Lavan switched her sister Leah with Rachel at the last moment. This was something Yaakov anticipated and had given Rachel signs to identify herself. Rachel, sensing that Leah would be embarrassed, gave the signs to Leah so there would be no embarrassment.
Later on in the pasha we see the story with Rachel, Leah, and the dudaim. When Rachel, who is at this point childless, asks Leah for the dudiam Reuven had picked for her Leah replies:
תֹּ֣אמֶר לָ֗הּ הַמְעַט֙ קַחְתֵּ֣ךְ אֶת־אִישִׁ֔י וְלָקַ֕חַת גַּ֥ם אֶת־דּוּדָאֵ֖י בְּנִ֑י וַתֹּ֣אמֶר רָחֵ֗ל לָכֵן֙ יִשְׁכַּ֤ב עִמָּךְ֙ הַלַּ֔יְלָה תַּ֖חַת דּוּדָאֵ֥י בְנֵֽךְ׃
She (Leah) said to her, Isn’t it enough that you took my husband? Would you also take my son’s jasmine flowers?
Although Leah gives the dudiam to Rachel, it is done very begrudgingly. Why didn't Leah have hakaras hatov to Rachel for what she did at the wedding and happily give the dudiam to Rachel?
