What is the name of your state? CA

I am the asst. manager at a small privately owner retail store. The environment isn't very formal and the relationship between managers and employees is more of a friendship than a boss employee relationship.

Recently I have not been getting a long with one of the employees and tried to confront her about it and asking her to keep her personal feelings and attitude towards me from the work place because it has become uncomfortable for myself and other employees and I didn't think it is appropriate behavior.

I spoke with the manager and we agree it would be best to all sit down and talk things out to resolve what ever her issues with me were. She told the manager she agreed to talking things out with us and coming to some kind of resolution.

However I came home to find a 3 page email from her cussing at me, calling me all sorts of names, and basically talking down to me and telling me how she doesn't like me as a person and listing the reasons why.

Even though as assistant manager I do not have very much authority but I don't think an employee should be aloud to send me messages life that.

I am now very uncomfortable with the idea of working with her and was wondering if there are legal grounds for her to be fired over this? Or anything I could do about this situation?

Thank you.