Well, first off, I am going to recommend calming down, after completely reading, and re-reading this, it has come to my understanding that you've found a piece if your past life. What I find peculiar though is the spirits and what not. If the two of you knew each other in a past life, how did it end up? If poorly, the manifestation of the woman spirit could be coming back to exact a revenge (all too common in human history, man cheats on woman, woman wants revenge). However, she wouldn't just appear out of the blue. She would have to know that Sam was with you.
This leads me to believe that she is following you, and may need your help. "Help" in this case, means to help her in letting go if something that happened 500 or so years ago. I would suggest finding her and trying to communicate. Ask her what happened, and see if you can render aid. Also see if you can get her to stop attacking your boyfriend. Once all is said and done, you should be in the clear. (And no, this isn't a plot from Ghost Whisperer.)