Is there a reason why you haven't spoken to your co-mgr yet?
If you haven't yet, write up a list of events, so that you aren't just complaining, and talk to her/him. If the co-mgr is a problem for you, talk to your store mgr. This person may think she is being funny, or is above reproach. Nobody deserves to work with someone who deliberately aggravates them. You might go on the wire, and see if there are any guidelines to define harrassment. If you feel that this person is acting unethically, you can call the ethics hotline. I think the # is 1-800-wmethics.
I called them one time, and was called back the next day. After that, the unethical behavior by mgmt, stopped.
Mad