But she gave it baaaackkk...
We don't talk enough about Elain being not only the first person to use Truth-Teller outside of Azriel, the first person he trusted TT with, but also the first person he trusted to keep TT safe.
The mandate from Azriel was: this will protect you, but you protect it.
We never talk about the fact that Nesta took TT from Elain and beheaded the King.
Did Nesta hand the bloodied knife back to Elain? Knowing that the dagger was Elain's responsibility.
Did Elain take the dagger that was just used to behead someone from Nesta's blood-covered hands?
Did Nesta drop it on the ground, and did Elain pick it up and carry it back with her to the camp?
She held on to it the entire time. Through the breaking and the reforging of the Cauldron. Through the unmaking of Amren. Through Rhys's death and resurrection. She held on to it not knowing if Azriel lived or died. Elain was the keeper of Azriel's legacy. And not only that, he WANTED HER to be the keeper of his legacy. If he died, he wanted HER to have Truth-Teller. Not his High Lord, not his brother and warrior Cassian, not his 500 year old crush Mor, not his High Lady. No, he wanted Elain to have it.
Elain carried that knife with her, maybe covered in King's blood, or maybe she wiped it with her handkerchief.
And then, when everything was finally over, and she saw that Azriel lived and survived, she handed it back to him.
But now, she wanted the protection to return to Azriel. She didn't keep it for herself. He was more important.
But yes, she 'gave it back'.