ability to sue employer under WA state employment laws for co-worker laying about my actions that resulted in termination

A co-worker lied about my actions and I was fired.: A co-worker lied about me saying I made an unauthorized purchase. This was not possible as I had a purchase order that the co-worker completed with the boss's credit card information and the boss's signature. The co-worker has responsibilty for getting authorization for purchases. I had no access to the credit card information. I merely submitted the completed purchase order to the vendor. The next time I saw the boss, she fired me without discussion. This was not the first time this co-worker lied about me to the boss. The co-worker also had created a hostile work enviornment that made it nearly impossible for me to complete my work. I had spoken and written the boss about previous incidents, but that resulted in my getting demoted.

Do you think I have any gounds for lawsuit for harrassment or defamation of character or anything else?