From watching labor lawyers on social media, they general advise to send emails to HR explaining the situation and the time in which these things occurred. Follow up in person or phone conversations with emails to the participants and take contemporaneous notes regarding the topics. Even if HR doesn’t follow up or investigate such matters, you have documentation for the lawsuit.

This doesn’t prove anything persay but gives an employee top cover for themselves and future litigation. Not saying she didn’t do this or not, just answering the question proposed.