Which woman has appeared the most times on the cover of Time Magazine?

Most Time Magazine Covers
Since it was first published, the most cover appearances upon the world renowned Time magazine has been by Richard Nixon (37th President of the United States) with 55 covers. The co-record holders for women are Princess Diana and the Virgin Mary, each with eight.

[From guinnessworldrecords.com 2004 article no longer online]

As of early 2016, Hillary Clinton has been featured on more Time covers than any other woman - 19 times.

https://www.washingtonpost.com/news/the-fix/wp/2016/02/04/the-19-times-hillary-clinton-has-been-on-time-magazines-cover/?utm_term=.46f16f0bcba4