I like the ideal she’s mortal but reincarnates

@Eriam  
Don’t most immortals age normally until they reach adulthood then they are basically ageless

@YenaMuffin: I don’t believe Cadence is immortal (we see her as a teenager when she babysits Twilight so we can assume she ages like a normal pony) so I can’t share that part of your headcanon.  
But I can still assume she may have outlived Shining Armor in her old days (or lost him earlier in the line of duty) and not stood his loss.

YenaMuffin  
Well it could also be my headcanon. In fact I have done the edit only for the fun ^^.
 
But anyway, your comment make me think to a fanfic about Celestia… this was quite depressing.

My headcanon:  
Being an alicorn, Cadence naturally outlived Shining armor. However, unlike Luna and Celestia, Cadence was a young alicorn, and wasn’t prepared for the loss of the stallion she had loved so deeply for so long. Shaken to the core, she would only wear black, the color of mourning. In the end, she cast aside her immortality, allowing the years to wear her down. The only thing that truly cheered her up in her final decades was her ability help mend the hearts of others, bringing couples together, and the knowledge that she would one day rejoin her beloved husband.

Let’s resume : She is an exiled puppet sovereign from a decaying dominion in which her husband has been killed through an guards’ insurection, thus creating a revolution which dived the nation into civil war… And she have lost her beauty cream full of Q10.