Facts, aging Chiaki to avoid controversy alienates a lot of people who preferred the younger version as weird as it is.
It honestly just made more sense story wise having her younger don't think it's weird. She wasn't sexualized in the slightest and it makes more sense trying to rescue a minor who you have known for years, that has no control over the shitty situation she is which really tugs at the heart strings. Versus now a girl your own age who has more outlets for help even if the fear and anxiety is still there.