Harmful threats from clicks staff member

My colleague and I were threatened by a staff member at Clicks in Melrose Arch . She said she is going to make sure that our lives are ruined , even if she gets arrested or dies. I have escalated the matter but not sure it's being taken serious enough. She followed me to the bank , and to our building office . Not only is this unprofessional but it's inhumane to treat people in that manner because you claim they don;t like you , we don't even know her name or anything . We now going to be living in fear, so uncomfortable . We will also be opening a case with the police , even though the lady seems very adamant about the point she wants to prove .