Rashi: To teach us that only one of the two Korbanos ¹ (the Chatas) ² is crucial for her to eat Kodshim (or to enter the Beis-ha'Mikdash)

Rashi and Rashbam: It implies that, until now, she was Tamei, as regards eating Kodshim and entering the Mikdash. ¹

Nidah, 18a: From the fact that the Torah writes, both here, and in Acharei-Mos, "Damehah", we learn that Dam Nidus incorporates four (two plus two) colors of Tamei blood - red, a shiny saffron plant, water mixed with earth and diluted wine, ¹ plus black - which is red blood that has gone off.

Kerisos, 9b: "Toras ha'Yoledes" teaches us that a Yoledes brings one set of Korbanos for a number of births, ¹ whereas from "Zos" we learn that this does not apply to where she bears one baby before the M'los and one baby after the M'los.

Nedarim, 35b: To obligate the Yoledes to bring a Korban Leidah, even if she is a Shotah - seeing as her husband brings it on her behalf. ¹

Sifra: In order too include a woman who gives birth to a 'Sandal', a placenta (containg no visible fetus) and a fetus with formed limbs. ¹

Ramban: Refer to 12:4:5:2.

Seforno: Because throughout her days of Tum'ah (including the days of Dam Tohar as she counts them on her way to becoming completely Tahor), she is thinking about the intimate parts of her body that produce babies and it is not therefore fitting to enter the Mikdash or to eat Kodshim.

Da'as Zekenim: It means that she is Tahor from the Din of the source of her blood; which normally renders her Tamei. Even though now it was Tahor, "ve'Taharah" is appropriate, since she was Tamei because she ate Kodshim and entering the Mikdash. ¹

Ha'amek Davar: She will be healed; the source of her blood will not spurt any more, even Dam Tahor, which weakens the body; it is a malady.

Targum Yonsasan: Bearing in mind that the Torah writes "ve'Taharah mi'Mekor Damehah" (plural), the Torah is saying that now that has brought her Korban she is Tahor both from her Dam Tamei (her Nidus) and from her Dam Tahor.