Honestly she probably crossed paths with mangos before but do you really think Liliana Vess would go through the emotional toil of asking what that weird fruit was? She would face the risk of being looked like if she was an weird/idiot by the natives of the plane? Never!
liliana CANONICALLY has no idea what a mango is

https://magic.wizards.com/en/articles/archive/magic-story/homesick-2016-08-29




