Huh.

That article supposes that Mary also chose the life she wants, but she couldn't love George if she never met him.

The world Clarence shows George is the world in which George was never born, not the world in which George disappeared around the age of 15. Mary could never "love George until the day she dies" in that possible reality, for in that reality she never met him.

It's still entirely plausible she could have wanted Sam. But I think the other way of looking at it is that Mary is instead motivated to choose the life she wants through George. She knew George as a girl, so she learned to pursue what she wanted. In George's absence, she never pursued anything, even Sam. And that resulted in the old maid librarian scenario. This is a Mary who has presumably rejected all suitors.

The author of the article says this too, that Mary has rejected all suitors, because there's no Mary-sized man. If true, that's not too appealing about her. So I'm going to need to rewatch the movie, to see if my idea is supported, because I'm not a fan of this idea by the article's author. It makes her arrogant. Mary is one of the good people of Bedford Falls, and to be inspired by George is the theme of the film. The effect of what one good man has on the people around him.