What if you can only prove that an employer asked an employee to have sex with her and did not ask again of the advance was rejected?

Examples of conduct that might create a hostile work environment include inappropriate touching, sexual jokes or comments, repeated requests for dates and a work environment where offensive pictures are displayed.  

 What if you can only prove that an employer asked an employee to have sex with her and did not ask again of the advance was rejected? 

Bennett-Alexander, D. & Hartman, L. (2015).  Employment law for business (8th ed.). New York: McGraw-Hill Education chapter 9

At least 200 words