Princess or Queen?

Some have already noticed that the woman shown to be Moses' surrogate mother in The Prince of Egypt is not, as the Bible states, "the daughter of Pharaoh" (Exodus 2:5), but Pharaoh's wife [0:07; seven minutes into the film]. Is this change merely an example of dramatic license (to promote Moses's relationship to the Pharaoh-to-be as sibling), or is there literary precedent? There is, and it is, yet again, the Koran.