Since I don't play the game (and likely never will), is she a robot that transforms into a human or what? And how?

Unbreakable said in comment #2584186:

Since I don't play the game (and likely never will), is she a robot that transforms into a human or what? And how?

robot with a human hologram

Unbreakable said in comment #2584186:

Since I don't play the game (and likely never will), is she a robot that transforms into a human or what? And how?

Spoiler warning on the 'how' part:
She is a part of a batch of military combat robots who's designed as intel/spy/infiltration operatives which comes equipped with holographic projection devices meant to disguise theirself as normal civilians. As the Hollow Disaster erupted, her batch effectively became useless and abandoned.

While the "human form" is cute, I would have preferred Aria to be only the robot one. The human version only serves to give fan artist as reason to not draw Aria, while pretending they are doing it.

I think the devs were scared she would not sell if she was only robot, so they made her human persona just to be safe.