u/Amitai2008

As we all know, when you first meet Shakra she calls Hornet a child, and our great queen Shakra could never make a mistake.

Hornet immediately feels the urge to correct Shakra, this action is usually done by kids ("I'm not small, I'm already 8" and such), we can see the comparison with an adult, when Hornet calls Lace a child she does not feel the necessity to correct her mistake, because she knows she's wrong.

Hornet is significantly shorter than her adult sibling, this proves that she still has room to grow, hence not an adult.

Hornet is about 2 times taller than her baby self, the insects in the game are humanoid, so we can assume that height ratio is kept.

(due to recent events this post might get me banned)