Depending on what's going on and the extent of it, women absolutely don't always know. Sociopaths and malignant narcissists can often have great social masks. They can seem like perfectly wonderful people. If you bond to someone you are convinced is a caring, honest, good person, you'll generally trust them to be where they say they are, doing what they say they're doing. Wives are often blind-sided. In retrospect, they often realize they missed some red flags, but because they loved and trusted their husband, they weren't on guard looking for red flags.