How long ago was it? Honestly I just don’t think you should drag this out. Your manager felt the need to say something to her so they did and I would just leave it alone. I would not bring it up to the manager unless your co-workers job is in jeopardy-in which case you then can try to vouch for her and say that you didn’t feel she was picking on you. The manager might just think she is messing around too much at work and wants her to be more professional. I would leave it alone for now, like I said unless her job is in jeopardy.