Oriana knew it was wrong, akin to selling her soul to the devil, but what else could she do? She could not remain ignorant and helpless, waiting for another witch capable of teaching her to appear who knows when.
She had to act, to grab this chance. She didn't care what she would have to go through, or even if she were to be blamed for patronizing the enemy.
As the saying goes, 'The end justifies the means.'
For her grandfather, Oriana did all reckless things which could have gotten her killed by now. She trespassed and robbed the merchant group in Azures Island. She scammed plenty of people, from her own village friends to the nobility of Karlin, even going as far as to deceive the royal family.
Everything else was negligible.
Now, aside from Phil, a new person had breached the wall Oriana surrounded herself with. It was Arlan, and to protect him, it was necessary for her to know how to use her powers. For that, she didn't mind stepping inside the enemies' den.