Theft of Intellectual Property

I had an inkling this had happened. Really, a very serious gut-feeling due to the character of the person involved and my previous generosity.
First of all, while I had a note that said "for personal use only, use for instructional or professional use is strictly prohibited" on my work, it was not formally copyrighted. Also, much of it could be considered "free-use" material as it if information that could be gleaned by anyone intelligent enough and schooled enough in the topic. And on top of that, I freely gave my materials to this person and others for their PERSONAL enrichment.
That being said, for this person to copy my work, at times character by character, is the lowest thing I have seen this person do, and she is someone of low integrity.
I was really mad when I saw the proof. Like call a lawyer mad. Then I thought about what it would accomplish. How can I prove she stole from me? It is true I have these same material dated before I knew her. And I wondered about when I made the information available to her. At the time, I trusted her and would never have thought she would do this. After all, I was (and remain) the subject-matter expert here. Would I give it to her today? NO. Would I give it to anyone else. Yes.
Just because this person is dishonest with absolutely no integrity, that doesn't mean I have to change who I am. I am a teacher, not an information hoarder.
I am angry about this, but also resigned. She took my stuff. But I think everyone who knows me will recognize it as my work.
Take what I had once freely given. Hope it makes you feel good about yourself, because I will never trust you again.