Elain is a Seer which means she has visions, a person who "sees" a possible future. As far as I can tell though, there is no gift of enhanced hearing that comes along with that.
- “Will I hear the earthworms writhing through the soil? Or the stretching of roots?
- “I can hear your heartbeat—if I listen carefully. I can hear her heartbeat, too.”
- “I can hear the sea. Even at night. Even in my dreams. (to which Feyre thinks "Even the town house was too far to hear anything from the nearby coast.") It would be impossible for a normal Fae to hear the sea from where they're at.
- “I can hear your heart beating through the stone.”
- “I can hear her—crying.”
- Also: Elain somehow knows the exact moment Cassian and Nesta need saved from the King. Almost like she heard what was going on.
- And: Cassian asks "so we track the Trove, how?" and Elain appears suddenly at the door to volunteer. She wasn't in the room, wasn't part of the conversation but heard him voice the question then randomly showed up.
If Elain is in fact an owl shifter (I've got previous posts on this) and has advanced hearing because of it:
- Their hearing is the best of any animal that has ever been tested. All owls possess extremely sensitive hearing, allowing them to hear low-volume sounds that are relatively far away
- with the aid of their incredible hearing.
Then I feel like its possible she heard exactly what went down between Rhys and Az on Solstice and returned the necklace to him based off the things he said.