>>279810055First of, she had a hard childhood and life, so being a "grizzled veteran" by 25 is viable.
But secondly, it related to what I said. In Japan and in most of the world prior to mid-20th century, a 25 year old was a grown-ass person, you were a legible man/breedable female by 16. On Titanic for example they didn't allow 16 year old boys on life boats because there were officially grown men already. In shonen manga in particular, if you're anywhere over 20, you're the 'adult person' archetype and can be a mentor, a parent etc.