To be more precise, she was a sister. A nun would be a woman consecrated to religious life who lives cloistered. While "nun" is used colloquially to refer to all women religious, the technical meaning is narrower. As many other commenters have noted, there is a culture of many women religious receiving advanced degrees. One of my college friends who got his PhD in political science at MIT was surprised to discover th…
As an aside, it always rubs me the wrong way when people insinuate the (Catholic) church is anti-science when the long list of contributions to science says otherwise.