Being of the Yellow Ajah means that Therva has some skill in Healing.
Her level of strength is described by "The Wheel of Time Companion" as 34(22) which is a quite low level in Aes Sedai hierarchy.
Therva is 138 years old. She was born in 862 NE and went to the White Tower in 879 NE. After spending eight years as a novice and seven years as Accepted, she was raised to the shawl in 894 NE.
She is present in the Little Tower when Nynaeve Heals both Siuan Sanche and Leane Sharif of stilling completely shocking everyone. Therva thinks that Fire could be useful in Healing problems of the heart.
Due to her skills at reading residues, she was one of the team chosen to investigate after the massive amount of the One Power was used for the Cleansing of saidin.
Some time after they report that they found a large hole where Shadar Logoth used to be. Reading the residues of Power they discovered also that a huge amount of saidin was used along saidar.