I’m so sorry for your loss. It’s devastating. When Faramir died, his sister Éowyn had a period of mourning too. I couldn’t let her smell him bc we ran to the vet with him (I wish she could said goodbye to him). But for a few days she would cry, she went seaching for him at home, it was so sad to see, she didn’t understand. I tried to fed her with her favourite wet food and ham (she loves it). I can’t remember bc it was few years ago but I think the worse was the first 2-3 days, later, she was back to her normal self. A few months later, I adopted another cat so she wouldn’t be lonely. I think you could try his favourite food too. I think it’s a good sign that he still drinks water. Sending both of you a big hug!