Board Thread:General Discussion/@comment-26273984-20150403165812/@comment-4010415-20150403183757

Well, that, and the song has the lines "All the joy that I had known for all my life was stripped away from me the minute that you died" and "I wasn't dreaming when they told me you were gone, I was wide awake and feeling that they had to be wrong. How could you leave me when you swore that you would stay?!"

So, I'm assuming they told Ruby that Summer died.

My headcanon for the "It's your blood that's red like roses" thing is that, maybe, they found her cloak and brought it to Taiyang, and it was covered in Summer's blood.