Something I made up and wish this was Cannon.
 
so What if Tempest has some Inner feeling for Twilight and Since she left, Twilight made Tempest her own Friendship Necklace to help Tempest Remember the pony who saved her life on the belcany on Canterlot.
 
 
(ABOUT THE NECKLACE)  
this Necklace can help Tempest Remember Twilight and made from pure Silver.
 
the Necklace has a star like symbol that simulates Twilight and has a Diamond heart to represent that She does in-fact love Tempest.
 
the Necklace does in fact has Powers. For Example when Ever Tempest is in Danger or in a situation that she can’t even handle. a Imagination Twilight comes for Tempest Aid Or can Create a Force Field From either A super Blast or explosion.
 
Twilight can Contact Tempest when Ever Twilight has A chance (Although Not in the show “Because Again its fan made”)
 
also the Necklace has a Side-Effect. So when Ever Tempest come across her Ex-friends or someone makes Tempest Furious or Worse. the Death of Twilight. Tempest goes on a Super Rage and Goes to a Dark form, Pretty much like Princess Luna as Nightmare Moon, Princess Celestia as Daybreaker and Twilight Sparkle as Midnight Sparkle. The only way Tempest can snap out of her Dark form. She has to Either Calm down, or bring up Twilight/ someone bring up Twilight (in a Appropriate way) and Finally Finished the job by killing her Victom.
 

 
either way hope you like this and maybe feel free to use it, and Once again make sure you credit me.
 
 
also artwork used for the photo here