God bless u .. my heart breaks for u . It is SO hard to lose a pet . My 2 Yorkies are truly members of our family . I agree w/Renee &Ginger ... depression can cause alot of physical issues that can result in death . Just like humans who have been married for 50 years , one of them passes away , & the surviving partner follows not long after . I don't know if u had an autopsy performed - it may provide u with some closure . However , in my opinion , ur little angel passed away of a broken heart .
I'm really sorry your Hayley died. It could have been that depression set in. Or like Renee said, it is possible she had a health problem as well. You didn't say what she died of?
Please don't blame yourself for this. Because it might look that way to you -that she died from the separation, but she could have been sick, and even had this coming on for a long time. You may not have known. Dogs often do hide their symptoms.
It could have been because they were so attached and she was depressed; well if nothing was physically wrong with Hayley. it would be very coincidentally if she would have died of a health condition, considering you had just separated her from her partner and all. I've heard of dogs dying of depression before, I'm truly sorry :( it's terrible losing dogs
best wishes,