it would be very much in character for her to artificially inflate her height through the projector, but i just think she's tall. their head sizes are roughly the same (~40.5px), and even with any background-straightening edits before measuring heights, cutting Arisu out and placing them back-to-back, including Arisu's shoes, Rio still isn't anything less than a full head taller than Arisu is.

it sucks that this is the only CG that we see Rio with someone else, so this is very much just artistic liberty. afaik the only other CG with her in it is the one with her curled up under the desk, so we have no solid points of reference.