To my pigs, if it doesn't smell like a guinea pig or mom, ignore it! The contrast with my parakeet's can't-tear-me-away reaction to a mirror is astounding!
My girls have a small mirror in thier cage it is a mirror designed to go in a bird cage and they often sit there and chat away quite happily to themselves.
I know but my parent say i have to use my current cage fo a while and it is only big enough for one piggie Id rather one pretty happy piggy than two misrable ones without room to run.