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.
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.