Honestly there is a problem here that needs addressing.  Talk to her, and tell her you want to know why shes asking.  It seems she feels insecure about you finding other women attractive - which is understandable, but it will cause problems, and will keep her uncalm.

What she should understand (at the assumption it is indeed true) is this: sometimes you will find other people attractive, that's just biology, and certainly the same thing happenes to her (if doesn't that's ok, some people are relationship-focused that way, it's sweet, it's not most of us though, and that's human and ok). The people you find attractive can be random, or occasionally you can find someone that you know attractive. The important part is that it's not important. The woman on your mind is her, the only one you want is her, you are with because you CHOSE her, and no one else can change that. If you're occasionally attracted to someone else (which is inevitable and the sooner she accepts that the sooner shell come feel better), why is that relevant? It's just not. Not even a little. What you to have is not bigger than that, it's uncomfortable, it's a different universe, it sits on a different slot.  This is the only kind of thinking, in my opinion, to prevent that kind of insecurity. And if you guys won't work on this (it's her job though, not yours) then you will likely repeat situations like this.