This is Harassment. The most inappropriate and totally unacceptable type of behavior in a corporate culture. You cannot ignore this email, this behavior has no place in any company.
What to do?
Most large corporations have an anonymous line to report such incidents. It is usually a website, so that you do not need to use your own name or email.
If her company does not have that, HR is the place to go. Some companies have a board of business ethics, that would be another option. (I met such a board when I married my customer, they were independent and pragmatic.)
Why do it?
Because this senior person is a threat to the company, its people, its customers and its reputation. It is not only your friend who was insulted, it is also the company that has been compromised.