Hostile Work Environment

I work in a hostile work environment but that is generated from a co-worker, not the employer. The co-worker admitted to the director and to me that they purposely and willfully do things to try and hurt me. Not physical things but work related things like accusing me of moving things in her desk so she can't find them. Or acusing me of talking about her when I do not. Or accusing me of charging at her while we pass in the hall. Or accusing me of being on long personal phone calls. I know this may sound silly but I don't know how much more of the accusations I can take. I've had to leave work several times because of stress. And honestly, mgmt and HR aren't doing very much because this has been going on for more than a year. Is their any hope for me to get this reconciled legally? Help!