I'm puzzled how your relationship could have been perfect when she says it wasn't. Or are you saying that her complaints are all since the FB incident, and both of you agree that it was perfect before then?
As far as secrets go, OUCH. No two people in the world, no matter how close, should share every little secret, whether it's past, present, future, imaginary, or a hangnail. Same goes for sharing towels and merging your CDs and eating off of each other's plate. If I had to say 'Honey, I just found an old friend on FB,' every time I found one (which is often, my whold HS class is popping out of the woodwork on FB), I think I would leave home. It's like being 12.
I'm a little worried that you have an idea of perfect that isn't her idea of perfect.
Again, communication. When did she feel you stole her love? When does she feel your lack of listening started? If you don't know those 2 answers, you have a lot of work to do, that and more.