Why did she say "I took off my robe"?
Rashi: I already got used to other matters. I cannot return to You - "u'Me'az Chadalnu Liktor l'Mleches ha'Shamayim..." (Yirmeyah 44:18). These ways were straight in their eyes. A woman who is Mezanah gives such answers to her husband, why she does not open the door for him. Because verse 2 began with "Ani Yeshenah... Kol Dodi Dofek", it concludes with an answer that applies to one who knocks on the door when people are sleeping at night.
Seforno: I removed my honored robe of Torah and good deeds, to indulge in temporary pleasures.
Malbim (Melitzah): Nefesh Shlomo answers, the Nefesh that merits Nevu'ah when it strips itself of physicality, it is clothed with tunics of light - a fine clothing made from Torah and good deeds that she engaged in them, via her understanding and actions in matters tied to physical things. Due to this clothing, she is not naked. Pure spirituality cannot be in this physical world without a garment. This is like the tunics of light 1 that Adam wore before the sin. (Also angels above, when they descend from their tasks to this world, they are transformed to be dressed in fine clothing, like Chachamim said.]
After the sin, Hashem made for them "Kasnos Ohr" (Bereishis 3:21), i.e. of skin; there, Ohr has an Ayin.
Why did she say "how can I wear it"?
Seforno: [How can I resume] to learn and to teach? One who learned, and ceased learning, this is harsher than all [who abandon Torah] (Pesachim 49b).
Malbim (Melitzah): In her sin, she removed her robe (she became mixed with robes of skin and flesh), and she cannot wear it again when she separates from her body, for it was already removed from her.
What is the significance of washing [her feet]?
Seforno: It was for pleasure.
Malbim (Melitzah): The body is like a shoe on which the Nefesh stands. At the time of Nevu'ah it removes the shoe, like intellectual matters removed from bodies - "Shal Na'alecha me'Al Raglecha" (Shemos 3:5), removing physicality. The secret of Chalitzah pertains to this. I already washed my foot, for pleasure, like a pampered person who does not walk barefoot - how will I get them dirty?! The Nimshal is, I cannot abandon the body, which is the shoe of my foot.
What is the significance of sullying her feet?
Seforno: [The way of Torah is,] sleep on the ground and live a life of pain, and toil in Torah (Avos 6:4).