For six years you’ve been like a dog worrying a bone, and the bone is called suspicion. This woman did you a favour by keeping you out of a relationship with a man who wanted to use you. She didn’t do it for you; she did it so she could be his secret tart.
You’ve wasted way too much emotion and time on this Casanova and one of his secret paramours. You figured him out long ago, and now you’ve figured her out as well. When we encounter people like this, the best thing to do is shake them off the way a dog shakes off water.