The best way to deal with a cranky coworker is to just be overwhelmingly cheery. This will either eventually break down their scowls or just piss them off in a really funny way.
"Heyyy, we got that in common too! Man down. We're real man-eaters, huh?"
She sticks another one on the wall, rubbing it into the concrete with her thumb to make sure it stays.

"This one is pretty, actually. It's got birds. Eastern bluebirds, I think. I'm gonna miss birds."
It's almost like she's not taking this very serious at all, but then she asks,
"Are you glad you did it?"