Tia is part of the Egyptian Coven vampires. She's Benjamin's mate.
As stated in Breaking Dawn book: "...the Egyptians all looked so alike, with their midnight hair and olive-toned pallor, that they easily could have passed for a biological family." "Tia, Benjamin's mate, was a quiet woman as well, though when she did speak there was great insight and gravity to everything she said."
Tia and her mate, Benjamin, seem more friendly and outgoing then the rest of the Egyptian Coven.