Answering my own question....
If the woman really is the one who killed her, I am thinking that this is a revenge/jealousy type situation from a relationship.
Marci moved on and her previous relationship couldn't handle that.
Or someone felt that Marci was a threat to their relationship.
I'm thinking like these cases of high school girls that kill their rival. That is what this is starting to sound like to me.
Or perhaps it was one of those "just wanted to know what it was like to kill someone" situations. I just thought that was a bit less likely since we are talking about 30 year olds, not 13 year olds. Not to mention she wouldn't be the person to target given her self defense training, if there was no specific motive to kill
her.
I haven't seen Marci's facebook linked anywhere. Here it is:
http://www.facebook.com/profile.php?id=554661805&ref=sgm