Can someone explain this passage on becoming a mature woman?

[GenkaiPower]

I read here as a translation:
"It's completely incorrect to say that the young lady is still in her teens because she's a bit mature, but you could also say that her inner soul is still young that she has difficulty in becoming a mature woman"

and was wondering does it mean they are a young adult or minor not yet? I wonder because to me I interpreted as she's a young adult not an older more mature woman? So young adult phase
Which is right?