i also noticed if you spam chiv spells like heal over and over .. if your casting while being webbed you don't get caught up.. don't work everytime but i guess its an option.
*cough*
Yeah, if she tries to web you while you're in the middle of a spellcast, the web fails because technically you're already "paralyzed" while casting the spell.
Navrey does make a noise a split second before she tries to web you, so you could try to cast Close Wounds as soon as you hear that noise. Spamming Close Wounds though, won't do much good, since you can't swing a wep while in the middle of a spellcast, and would end up butchering your damage output by trying to spam Close Wounds.
Mages on the other hand, can keep their distance and spam away on her with Flamestrike, the long cast time can protect you against most web attempts. I have a Bard/Mage friend with 100%+ SDI, and he hits her for 300+ damage Flamestrikes while she's Discoed, and on the rare occurence that she does land a Web on him, he just area peaces during it.