Time is what she needs. Giving her more to do might help. Maybe new scratching posts or toys to keep her attention.

Personally, I'd adopt another cat. So as soon as YOU are ready to do so, I'd start looking. Find a cat that is not too young because that might be too much stimulation for Lucy, and find one that had a layed back personality so as to not threaten Lucy.

I am sorry that you both have to go through this loss.