I agree with most of what has already been said. I'd just like to
add that if she ever does come to the realization that you are a
CD, or even if you confide in her at some point, then she will not
only have to come to grips with your keeping this secret but also
that you "tricked" her and essentially took something that is
extraordinarily personal. For this and the other reasons listed here,
I wouldn't ever attempt this.

Jackie