You were killed by Amarantha 40 years ago...for no reason really, except you were Rhysand's wife. You were resurrected a week before the final battle with Hybern because Rhysand thought Amarantha killed you because you knew something that could be useful against Hybern, it turned out you were murdered at Amarantha's whim. As were your two teenage children you had with Rhysand

You avoided Rhysand for that week...because you didn't want to ruin his new life with Feyre. Feyre respected and admired you for that even though she knew you and Rhysand still had feelings for each other. Feyre often heard you waking up at night in "your room" in the tent as if Amarantha was killing you again, stabbing you in the chest, which caused blood to pour into your lungs and throat...and that was it

After the battle Rhysand was badly wounded. Feyre and you got to him as fast as you could...