Elizabeth Taylor and Marilyn Monroe with 14 each
Elizabeth Taylor with (I counted) 14 covers:
https://www.originallifemagazines.com/olm-search/?searchMonth=&searchYear=&search=elizabeth+taylor&coversOnly=coversOnly
Marilyn Monroe 14 times (six were after her death):
https://www.originallifemagazines.com/olm-search/?searchMonth=&searchYear=&search=marilyn+monroe&coversOnly=coversOnly
I enjoy playing Trivial Pursuit™, the board game. When I do, if I miss a question, I try to pay attention to the correct answer, so that I can learn something. One of the questions I missed some time back was this one: “What woman's picture has appeared on the cover of Life magazine more than any other?” I thought of several possibilities: Marilyn Monroe, Jacqueline Kennedy Onassis… perhaps Elizabeth Taylor or Princess Diana…. all of them wrong. The answer? The woman whose picture has appeared on the cover of Life magazine more than any other is… Mary, the Mother of Jesus.
stpaulsumc.net 2003 article, no longer online
I believe this is an error. Using Life Magazine's cover search engine, which only searches through to 1972, I found absolutely nothing for the Virgin Mary. I searched keywords Mary, mother, virgin, Jesus and Christ.