Empty promises.

It was a selfless sacrifice and now his ghost haunts her, her every waking moment.
It was a striking reminder that he was gone, and she'd never truly see him again. She needs to move on, but in reality, she can't.
Not when she was dying from a broken heart.

What had originally stemmed from an innocent promise between childhood friends, broke many more promises that followed between them before they even had a chance to be completed.

Instead of seeking professional help like therapy, she doesn't want help, she doesn't wanna get better.
A part of her knows that if she heals and moves on, Azrael's ghost will forever be gone and she can't stand the thought of that.
The thought of him being gone forever is just something she cannot accept.
Lucia still needed Azrael in her life, but he was gone.

His life cut short before it began, and it was all her fault.