Why did she say "Anochi Rus Amasecha"?
Malbim: Do not think that this is lewdness for a woman to surround (hold) a man. I am your Amah! Just like there is a bond between an Amah and her master - he is obligated 1 to be Meya'ed (marry) her. So there is a bond between us, due to the Mitzvah of Yibum!
No verse obligates him to marry her, but Rashi expounds "b'Vigdo Vah" (Shemos 21:8) - if he will betray her and not do Yi'ud, and also her father betrayed her via selling her to such a man. (PF)
What is the meaning of "u'Farasta Chenafecha"?
Rashi: You will cover me with the corner of your garment; this is an expression of Nisu'in.
Malbim: (a) This is a metaphor taken from birds, which spread their wings over their mates at the time of intimacy. (b) She hinted that this Bi'ah does not transgress the Torah - the corners of a garment, with Tzitzis, save from such a Bi'ah, like it says in Sifri 1 . Just the contrary, this Bi'ah is a Mitzvah, for you are a Go'el!
The case is brought in Menachos 44a. (PF)
Why did she say "Ki Go'el Atah"?
Rashi: You can redeem the inheritance of my husband - "u'Va Go'alo ha'Karov Elav v'Ga'al [Es Mimkar Achiv]" (Vayikra 25:25). I and my mother-in-law need to sell our inheritance; it is upon you to buy. Acquire also me with it, and the Mes' name will be called on his inheritance, when I will come on the field, they will say 'this is Machlon's wife.'
