I pulled a card from my deck at random because that's how I've been doing things lately, and the HP was the card that I pulled. I'm posting this without having read through the other posts in this topic because I wanted my interpretation to be fresh.
She's a young woman (note the flat chest while other women in this deck have rounded breasts) wearing "modest" clothing that covers her body from head to toe (as far as we can interpret from this image). The only parts of her body visible are her hands, her face, and a little bit of her hair.
The crescent moon in the lower right-hand corner could be waning or it could be waxing, but given the apparent age of this particular women, it is safe to interpret that it is waxing as she grows older (becomes more fertile, more vibrant, as time goes on). She wears the symbol of the triple goddess on her hood, and the three pomegranates above her head may represent the trifold nature of her position. She is, at once, Maiden, Mother, and Crone.
Her expression, to me, bears a hint of scolding, at least in today's interpretation of the card. There's some admonishment there that one should read the contents of the scrolls in order to gain the wisdom and truth of the high priestess.
I see her as an eternal virgin, devoted to the goddess and ripe with wisdom and knowledge rather than with children. She's wise beyond her years, but barely more than a child herself.