How does Hester transform herself during the encounter with Dimmesdale in The Scarlet Letter?

Whenmeets within the
forest (in : "A Flood of Sunshine"), they speak for a while, especially after she
confesses to him that(who's been torturing Dimmesdale) is her long-missing husband.  Although
Dimmesdale is angry at her at first, the pair eventually begin to make plans to run away
together on a ship, leaving Boston forever, because they are still very much in love.  Feeling
joyfully for the first time in a long time, Hester removes the scarlet letter from her chest and
takes off her cap, releasing her long hair onto her shoulders.  In this moment, "A crimson
flush was glowing on her cheek, that had been long so pale.  Her sex, her youth, and the whole
richness of her beauty, came back [...]."  The sun begins to shine on her as it has not
done for years, and she seems to come back to life.  She did not realize the terrible burden of
the scarlet letter until she removed it and felt the freedom of its weight having been lifted. 
She smiled a "radiant and tender smile."  However, when she must replace the letter
and cap, they functioned like a "withering spell," and the radiance and youthfulness
that Hester exuded without them melted away.