I am so sorry to hear about Nala! Dogs can be so intuitive. Maybe Jernee knows.

When our Sophie died last year, her sister (not blood-related but had been together for 11 years), pined for her. Syau wandered the house looking for Sophie and made the most pathetic crying sounds when she slept. When we walked, she'd keep look behind because when Sophie was sick, she was always walking behind a little ways, not able to keep up with Syau in the front like she once did.

I had Sophie cremated and kept her collar. In desperation to make Syau stop mourning, I showed her the collar. She sniffed every inch of it. Never again did she look for her sister around the house. Never again did she cry in her sleep. Never again did she look behind while walking.

Sophie's collar obviously conveyed a message to Syau. It's all beyond our understanding.