Daas In Kiddushin

ויצאה מביתו והלכה והיתה לאיש אחר 

Rashi in Yevamot (19b) says this possuk is the source for how we know that kiddushin must be known with the willingness of the woman - הָלְכָה וְהָיְתָה לְאִישׁ אַחֵר – מדעתה משמע.  There is a twofold question on the Rashi.  1.  Why do we need a possuk, why is this different from any other kinyan where דעת מקנה is required?  2. Rashi himself in Kiddushin (44a) says that דעת מקנה is the reason that the woman's acquiescence to kiddushin is required? 

The Achronim say that the answer lies in the context of the Gemorah in Yevamot.  The Gemorah there is discussing if מאמר must be done with the acquiescence of the woman or can even be done against her will.  The Gemorah says the Rabbanan hold you need her agreement to go through with מאמר just like her agreement is required for kiddushin.  If the only reason that a woman's דעת is required in kiddushin is because of דעת מקנה, that wouldn't make sense to equate to מאמר because she is not the מקנה.  Therefore, Rashi understands that the דעת of the woman is an integral part of the maaseh kiddushin.
What difference does it make that the דעת of the woman is required from the possuk?
The Smag (Asseh 48) holds that if someone forces a woman to accept kiddushin, it is not valid.  Why would the kiddushin not work, why is it different from any other kinyan where if you force the makneh to do the kinyan it works because under duress they agree to do the sale (תליוהו וזבין)?  We see that the Smag holds the possuk is coming to tell us that its not enough with the regular דעת מקנה for kiddushin.  The possuk comes to tell us that it's not enough for there to be daas to go through with the kiddushin, but that she must desire for the kiddushin to be done.