We had a similar(ish) case happen on my street recently, there was a little old lady named Rita who I had known for years. She'd been getting on in her years but she wasn't ill or anything like that, she also had this dog called Gus. Anyway, Rita went away for a few days and she couldn't take Gus with her. While she was away Gus died and when my step-father went to check on him (he was caring for him in Rita's absence) he found him curled up on her bed. When Rita's daughter broke the news to her she passed away a few days later. I'm not sure if it was for any medical reason since she was a perfectly healthy woman for her age, it could've been but I dunno. She loved Gus to bits so I'm assuming the shock or the fear of coming home to an empty house just got to her. Sucks really, she was a really nice woman. :(