Why does it say "Shadud" (masculine)? The Navi speaks to a female; the rest of the verse is in the feminine!
Radak: Some say that this is like k'Shadud (you are like one who was plundered) 1 .
Radak: Sometimes the verse address Keneses Yisrael in the feminine, and sometimes in the masculine, like I explained above (refer to 3:5:4:1).
What is the question "Mah Ta'asi"?
Radak: When the downfall comes, how will you save yourself? Now you adorn yourself without concern for the evil that will come on you and you are not humbled. You should have been humbled in front of Hashem, and worn sackcloth and repented, and not wear scarlet and gold ornaments! So Yeshayah said (22:13) - "v'Hinei Sason v'Simchah Harog Bakar v'Shachot Tzon
Why does she dress in scarlet garments?
Rashi: It is to beautify herself and find grace in the eyes of the plunderers.
Radak #1: She has no concern for the evil that will come on her; she is not humbled.
Radak #3: Yisrael doing idolatry are compared to a harlot, like I explained above (3:1). A Zonah wears nice garments and paints her eyes so men will desire her. So Yisrael did like Nochrim, to serve their gods and dress like them to aggrandize and glorify themselves in front of them, and [went in] beautiful chariots so the Nochrim will love them, and say 'they are like us', and love them.
Malbim: This is foolish. They already plundered everything else she has. Surely they will take also this!
Why does it say "Sikre'i"?
Rashi: Mascara appears to widen the tear (opening) of the eye.
Radak: Constantly painting the eyes tears them.
What are "Ogvim"?
Radak citing Targum Yonasan: They are people who desire you. This is like "va'Tagav Al Me'ahaveha" (Yechezkel 23:5) and similar verses.
Why does it say "Nafshech Yevakeshu"?
Radak: You thought to be save yourself. Just the contrary! You removed your trust from Me, trusted in idolatry and resembled the Nochrim in deed, so they will love you - they despise you, and seek to kill you!
Malbim (29-31): All the cities around Yerushalayim fled to Metzudas Tziyon. It is as if the entire city fears, except for one harlot who relies on her beauty, thinking that the enemy will desire her beauty (of Tziyon) and have mercy on her. They will not desire your beauty, rather, to kill you!