People seem to say that Ultimecia is Rinoa, by the fact Squall grew old and she did not. Trying to use Time Compression just to see Squall again. I find this hard to believe since Sorceresses like any other person grows old. This actually is stated in the game itself, by Edea.

It seems Edea has received her powers from Hyne at the age of five, perhaps this might be the reason why she didn't want one of her children to become on, because she knows how it must feel. If sorceresses do not age, how come we have Edea as a adult?

She received her power as a child, later received another sorceress her power 13 years later. Not is sure how old she was then, but we can conclude that how young she might look compared by Cid, is the fact that she must be in her thirties.

Perhaps this sentences are the proof on that Sorceresses do age, like us humans can, because as far as I know they are humans aswell, just higher skilled in magic.

"I received the powers of the previous sorceress at the age of 5.

"I first became a sorceress when I was a child. And once again...13 years ago."

So as far as I know, that theory asset is wrong, because it has been answered by Edea herself, the fact that sorceress do grow older.