^^That could go very wrong in a multitude of ways. If she really doesn't like it, catastrophe could happen.
Drat, I was gonna bring up trust until I read the last sentence of your post. Yeah, if its not her fetish, the control route wouldnt work.
If she's gagged shes completly at your mercy, she pretty much has to have complete trust in you. When you choose to love and care for her even when shes in that state of helplessness, she'd feel closer and more intimate with you than ever. I would think thats the best route to go, since I think that at a subconcious level thats why a lot of people enjoy being gagged, as well as gagging others since it shows that they have a lot of trust in you. Idk, maybe thats just me.

I don't know, if nothing else it could just be that being gagged isn't her thing. :<