[btschaegg]

If she has little experience with video games, Journey and Gris might be good candidates.

For a more "technical" argument how gameplay mechanics can be a unique way to deliver an emotion to the player (arguably a major part in the role of art): Brothers: A Tale of two Sons. You'd have to make sure that she finishes it, though (estimate: ~3h).

Two trippy games that defy categorization (but won't be good examples for someone not willing to learn mechanics/logic in depth): Thumper and Cocoon.

[Gerard0]

Never heard of any of these. Checked them out and they all look great. Hard to decide but I think I will include one of yours. Thanks a ton!

[ChoGGi]

Going into it blind; Journey is a special treat.

If she is a fan of detective stories, then you wish to look into L.A. Noire or Shadows of Doubt.

Ori and the Blind Forest

Jusant or Tiny Glade have a distinct look.

Edit: Not art but for two player games, try Lovers in a Dangerous Spacetime, Untitled Goose Game, or Trine.