Lady Hightower

Not seen since she was a young babe, Lady Hightower makes an unexpected appearance at the Heir's Tournament. Bringing with her daughters, Taelaenya, Vaena, and Valaerys. She is relatively unknown to the whole of Westeros, save for Houses Hightower, Arryn, Targaryen, Martell, and Velaryon. Her sudden reappearance causes shock and curiosity to ripple through out King's Landing.

Who is this mysterious woman, and what connection does she have to House Targaryen?