I finally got around to finishing Vattu yesterday and apparently she was like 27 or at least in her mid 20s by the end? I am really bad at picking up on subtle references to time passing, so I thought she was in her late teens or something.
It doesn't help that the main difference between her character design when she was 9 and by the end is being taller and having a longer head (makes sense in context), but considering the politics is grounded it makes sense that the revolution wasn't helmed by a teenager.
When I read books or comics I imagine every character has a different voice actor like in a radio drama and I had given Vattu a deeper voice for book 4 based on the vibes, so serendipitous I guess.