Shirlly had a tragic childhood.
Her parents were normal and loving till she was 5 years old, managing to hide the worst of what was happening in worlds (both of them).
At a playgroup her parents met with another couple that were Mage students, with their own child the same age.
As the two couples became friends, the students started introducing Shirlly's parents to a little light mana residue,
No one really knows how things spiralled out of control but within two years both couples were on hard crystals and had become hopelessly addicted and useless to their society.
They had become "Wretched"
The child of the Mage students died from neglect and the same nearly happened to Shirlly.
She was taken away from her family at age 7 and by the age 8 her family had died from their addiction.
She vowed never to directly use Mana.
She entered the city guard at a low level doing under cover work to help stop the bad mana dealers.
There she saw things that cemented her anti mana beliefs.
That along with her undercover work led to her taking the Rogue path.
She is dedicated to the Horde but is more concerned with threats within than external ones, (Betrayal and so forth).
She tends to be a tad self righteous and accusatory to all classes that use Mana, feeling that they are being weak and that the Mana is using them not the other way round.
She has little empathy for her own Race and its history.