Its your duty

Thanos wanted his offer to be worse, but he had to think quickly. Jenna stood there waiting, playing with the purple sparks that flew from her fingertips, she was fascinated, bewildered by her power. The power leaving her didn't hurt, sometimes she was unaware of it leaving but with further training she would be able to control it. When Ebony placed the memories in her mind, she believed that she was trained to understand so therefore she understood.

"I will grant you freedom, but I ask for one thing in return."
Jenna shot her head up at Thanos' words, freedom?
"Didn't I already have freedom?"
"No, I freed you, then you became my daughter, I'm offering you eternal freedom, I advise you to listen."
"Well seeing as your not going to let me leave without a fight" she turned to Ebony, "and I really can't be bothered to fight today because i was FREED" then she turned back to Thanos, "I'm listening...Father."
Thanos smirked, he was getting what he wanted.
"You work for me now, it is your duty to collect all six stones and return them back to me, after, I will grant you freedom like you have never known before. Being trapped in those stones must have been painfully boring."
"It was boring actually, anyway, how do I know you will keep your word" Jenna interrogated Thanos.
"Oh don't worry, Master always keeps his word" Ebony sneered.
Taking a deep breath in, Jenna gave up on her argument and decided to give Thanos what he wanted.
"Very well then, just remember, I can destroy you and your puny little planet with the snap of my fingers do you understand!"
"I do little one, now, be on your way, time is ticking."

Time? Jenna had all the time she wanted, she was immortal. Her initial plan was to lazy around for the next five thousand years until Thanos was on his dying days, then he would be gone and freedom was hers. However, she didn't know how invasive Thanos and his 'children' were going to be for the next few thousand years, and how sweet her freedom would taste.