Even though she did grow to like Reina quite well after getting acquainted with her, she couldn't just throw away this golden opportunity of getting a powerful comrade under her rule. Her desire prevailed over her morals.
Her utmost priority was still getting as strong as she could, and Xenos was a prime candidate for that goal.
Aria took a deep breath in before beginning to manipulate her mana stealthily and mess with the settings of the cage.
On the other side, Reina already began to feel disturbances, but did not connect the reaction with Aria's doings yet. She still though that it was part of the price she had to pay for overexerting herself that much fighting Xenos and maintaining the troublesome spell.
Meanwhile, Aria continued to do her thing and finally managed to trigger the locks open after fiddling with it for some time. She ignored the strange stares that she received during the time that she speedran the task.