Harassment in Workplace

My question involves labor and employment law for the state of: WI. Hello, recently my wife received a harassing note in her workplace. She came into work on a Tuesday and there was a letter under her keyboard that featured a bloody vagina and several phases that were sexual in nature. She asked the people around her who put it there and was told it was one of her co-workers Hailey. She was told that the note was put there Monday night and several of her co-workers saw Hailey put it there. She was surprised and offended as she considered Hailey a friend. She took the note to her boss who agreed it was offensive and stated he would take it to human resources. Later he interviewed Hailey and reported to my wife that it was a "joke" and Hailey didnt mean any harm by it. My wife didn't take it as a joke and was uncomfortable going to work the next few days to avoid being around Hailey. Long story short, she has not been contacted by human resources about this and Hailey is still employed. I know my wife would normally not be followed up with regarding the steps HR took, if any, but it appears nothing has been done as Hailey was at work just today. Do you think this should be a terminable offence for Hailey? What steps do you think my wife should take next? Thank you

Harassment in Workplace