To fight the other Six Gods is something that Enchantress could face. To behead the Oracle and challenge Destiny is something she is fully ready for. But to change the Destiny of the Old Soul is not something that Enchantress can do.
It was the Old Soul's words that reverberated through Enchantress's soul in the first place. The Enchantress realizes if she chooses her own Destiny, the Old Soul will lose everything. The garden would have been withered.
The Enchantress throws the head of the Oracle and falls on her knees. Everything that she has gone through is now vanished into thin air. The Enchantress would need to give up on herself, so that the Old Soul may receive the place in Valhalla.
The Enchantress opens her arms wide and stares at the shattered sky, ready to receive the Destiny she was meant to have.