I would recommend finding an allergist and having her tested for allergies before the surgery, if she hasn't been tested recently. Allergies are horrible on my sinuses (I was sleeping with a goose down comforter and found out I am allergic to feathers!) and I haven't had polyp problems, but I have had chronic sinus infections and blockages until I started taking Singulair, an antihistamine everyday, and now, sinus washes with a neti pot. Last time I had a bad infection, I had to do a nasal neb with antibiotics for a month to clear it up.
If allergies are to blame (or partly to blame) and aren't treated, it is very possible that she will be right back in the same spot not long after surgery.
I almost had nasal surgery one fall for a deviated septum, until my nurse recommended me to not to have it, since that was my only problem (no polyps). By spring, my catscan was clear, and then I started taking antihistamines and it hasn't been recommended since.
However, like I said, I had no polyps, but if I had, I <i>would</i> have done the surgery.
Sometimes you just get so used to feeling a certain way, that you don't even realize how bad you do feel. When my sinuses cleared up this last time, I remember thinking "Oh yeah, that's what air in my sinuses feels like- gosh." I had truly forgotten what that "normal" sensation felt like. It's possible that is what is going on with you daughter and her blockages (I hope not, but it's possible <img src="i/expressions/face-icon-small-wink.gif" border="0"> ).
Good luck!