Who is she?

She is Mary Magdalene, the painting is called “Magdalene with the Smoking Flame”. It is said that they put this painting because Magdalene represents the 로스트 bride of 예수님 and is also the archetype of the "Sacred Feminine”.
link
I read about this in the Da Vinci Code, it was very interesting.

Saint Mary Magdalen with the Smoking Flame is an oil-on-canvas 의해 French Baroque painter Georges de La Tour, painted in 1640. This version of the painting is currently held and exhibited at the Louvre in Paris.

That looks like the painting from the little mermaid!