1) This is not doxxing.
2) The author found her identity in her tweets -- she included her full name and other info. Anyone who "followed" her could have found her. This is not doxxing.
3) He called her husband's company to ask for a comment or response because of the contrast between her husband's work and her writings. That isn't doxxing, either.
4) He did not publish any private information about her. Not her address, phone number, email address.
This is an example of journalism, not doxxing.