What does B-girl mean?

Female B (ぉとめ) means "girl", which is between Lori and Yujie.

Not old, not married.

And pure. (pure+pure natural feeling)

The Japanese pronunciation is: o to me (oh-set-sell).

Common in constellations.

Block b runs from August 23rd to September 22nd.

Also known as Virgo, which is what China called Virgo.