I bought my fiance a fake diamond ring...now I feel guilty?

Okay, a little advice. And you listen to this, 'cause I am a girl and I know how we girls work. You tell her it is fake, because if she finds out you tried to replace it, you will have a lot of extra explaining to do and she will be mad because you lied to her twice. And she WILL find out sooner or later if you do switch them because the rings will look different, and she will be wondering where the "real" ring is. If you switch the ring, it could mess the whole relationship up. That is not a good thing.