In my experience, cats want warm bodies to sleep on/with, they want tuna, and they want your attention at the most inconvenient times – when you're in the bathroom or on hold or when someone is at the door :D. I suspect what she needs most, having just lost a feline companion, is a cuddle buddy. Can she sleep on your bed with you? That's probably the best healing she can have.
Honestly, Roxy is sleeping with me. Agatha is getting braver about hopping into bed with us, but hasn't actually slept there since Roxy's arrival. Between Sherlock's death and Roxy's arrival, Agatha cuddled with me every chance she got. This evening, Agatha started following Roxy everywhere. So, I think/hope that's progress.