Tadukhipa, Princess of Mittani, arrived 2 years before the death of Amunhotep
III in year 36. A high price had been paid by her father, Tushratta, for the
assurance that his daughter would be 'Queen of Egypt'. Tiye, Amenhotep's Great
Wife, was still alive and hardly likely to have entertained the thought of
stepping aside for this girl. He had just married Sitamen II in year 30, raising
her to the dignity of "Great Wife" alongside her (?)mother. Amenhotep may have
decided to have the princess wed Akhenaten, his co-regent. She would then attain
a high status as 'Second Wife', and this may have somewhat appeased her parents.
(Although he must have had an even more important second wife whose name would
be written in a cartouche.) The canopic jar lid below represents Kiya, these
originally being made for her. They ended up in tomb KV55, altered for reuse by
a king.
If she was a foreign princess, she could'nt have hoped to attain a high position unless she became a wife and mother, preferably to the most direct heir(s) alive, after the great wife and any other eligibles. If she was the mother of heirs, then it is strange that Akhenaten did not foster any relationship with her father, or come to his aide when the land of Hatti decided to conquer the mittani kingdom! (Unless she died before these events happened).
I have long entertained the thought that, if she was not Tadukhipa, she may have been a daughter of Ay[a]'s. The name similarities are striking, she is nowhere mentioned as the daughter of a King, and she appeared on the scene about the same time as Ay's rise in status.
A point in consideration against the Kiya/Tadukhipa theory; As a wife of heirs, she would assuredly have been raised to the dignity of 'second wife', which would have entitled her name being written in a cartouche. It is not, nor has it ever been found so written, as Kiya or Tadukhepa. If she was a daughter of Ay, a noble's daughter, no matter how powerful the father, would've been considered lucky just to obtain a postion in the harim.