I've had this happen to me actually. People straight out told me they were psychopaths. And also that they had never told anyone else. I think in my case at least, it was a situation of like-recognizing-like. They could tell there was something different about me (alexithymia) which was similar enough to what was different about them (psychopathy). The two do share traits. They were curious as to how I'd react I suppose, and curious if I was a psychopath too, as the condition is so rare.
Perhaps your boss was trying to suss out if you were like her, and if so, she would have to handle you differently than the other employees, because your mind works fundamentally differently if you were.
I suppose that's part of good HR skills. Telling you about herself may have prompted you to do likewise - but then again, that sort of move rarely works on a sociopath, either, so perhaps she was testing your reactions to assess what you were and how to handle you.
The information may be helpful for you however - if she is correct and she is a sociopath, you have a nice blueprint of predictability about some of her behaviours and motivations, and you can deal with her in a more appropriate fashion with that in mind. I've never found psychopaths to be a problem if one is sensible of their nature, and responds accordingly. You can't treat them the same and have the same basic expectations of them as you would normal people. Others seem to be scared of these kinds of people because they believe they are going to hurt them. And true, with the psychopaths I knew, indeed you could not rely on any basic emotional barrier to stop them doing so, because they don't have any. That noted though, understanding that means you can more easily understand their real motivations, and dodge any problems.
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Alexithymia - 147 points.
Low-Verbal.