What is the significance of "Shoshanah Bein ha'Chochim"?
Rashi: The thorns puncture it, and it always stands in its beauty and redness.
Seforno: A rose grows only amidst thorns.
Malbim (Melitzah): Hashem says, you Bnos Yerushalayim (bodily powers) are like a rose; the branch on which it grows is full of thorns. She must lift her head over them, lest she mix with them, and they will puncture her. So the physical powers that the Nefesh is above them - they are like thorns that puncture the Kadosh rose when she mixes with their company, and they ruin her beauty and glory of her Kedushah. She must be elevated over them and not mix with them. Malbim (Mashal) - so you must beware lest Bnos Yerushalayim entice you to love Shlomo.
What is the comparison to "my beloved among the daughters"?
Rashi: They entice her to run after them to be Mezanah like them, after other gods, and she remains in her Emunah.
Seforno: She does not turn to Me in any other way.