I think Square may have meant to use this story of R=U but decided against it in the end but still left all the points hidden in the game. Ultimecias castle being located right were Rinoa and Squall promised to meet, Its one of few explanations as to why Ultimecia would actually want to compress time, They both have angel wings and the colour change from white to dark would easily mean the change of mind from good to evil, Theres the fact that she wields Griever which was a present Squall gave to her, and also I think they have the same hair colour. If you're really interested look for a bunch of threads in this forum that went over it in much greater detail with more evidence.