I am sure if she sent a message to a "boyfriend" it would be a message, not a post. If it is a message, only the person she sent it to could view it. Maybe the person she sent it to shared it with LP. If it was really her and not another KC imposter.
You can foward myspace messages to other people, maybe that is what happened. I hope she did do it and they take her back to jail for communicating a threat.