No one knows for sure either way as to whether or not she knew the depth of his darkness. The human brain works in such mysterious ways. It must be excruciating to have this slapped in your face. Their probably was classic "tell tale" signs of this guys deviant ways. At the same time, she, not wanting to believe her spouse to be capable of such evil, could have easily blocked these exact signs out.
I truly believe that the brain does this under extreme stress so not to bring forth a " nervous breakdown." It's both normal and easy to manipulate your own thoughts. The majority does this, on a much smaller scale of course, on a daily basis.