When had it all started? Not even she could remember at this point. She just barely remembered that she used to be a person, but that fact had been erased from history the moment she became divine. She was the only one who knew that she used to be human, and there wasn't even proof of that. It was so long ago that, as for what kind of twists and turns had led up to her current state, not even she remembered, but there was no doubt that she'd rewritten existing space and become a god in the end.
After that, the first thing she did after becoming god was to create an entirely new universe. Next, she created a planet with a suitable environment for creatures to live in before trying her hand at creating life. However, this was where she stumbled. She housed enough destructive power to make short work of the universe itself, but she had no ability to create a new life.
Why? Because to her, life was far too fragile. It was far more transient than what she was able to handle. The act of composing a life was so complicated, like a puzzle that needed to be completed to move forward. However, even touching one of the parts of the puzzle was hard for her. As she was, even if she wanted to create life, she would come out of the endeavor with nothing. With no other choice, she decided to move the living things she wanted from her former world to the one she'd made—named Midgar—little by little, and have them propagate and flourish in the new environment.
Time passed, and when species with similar intellect and forms to humans on Earth eventually sprouted forth, she was so happy she danced a little jig. She loved humanity. If they wanted something, she answered, and if they wished for something, she gave it to them. That never changed, even after someone ate the forbidden fruit filled with evil concepts that she'd forbidden them from ever touching.
I love you all. I want you to be happy. I will surely lead you to happiness!
With that wish, she granted humanity everything they wished for.
But… Why? I wonder why? The more I give, the more I fulfill their wishes…
Humanity's standard level of happiness and fulfillment continued to go up, and the higher it went, the less they were able to feel happy.