Does the co-worker think you said something to the manager? If she does not think you said something then maybe the manager just saw the way she kids around and think she’s going overboard for the workplace. As a business owner myself, while I want my employees to enjoy their job and have a good relationship with each other-I also do not tolerate messing around at work. I want my employees to just get the job done, get it done right and be respectful towards each other.