Luna?

[Sephiroth]

Well true, but the interview you linked interns the E3 2013 trailer. Since then, the character designs don't seem to have changed and this girl looks different enough to be Stella's sister.

I don't get your point here. It just means she was redesigned earlier than just last week. And when she was redesigned she could have retained some of her old traits but gotten new ones as well which can be very well the reason why she has that "sister" feeling for us. There are also flashbacks in the story so we don't know when the time of that picture actually is - though it is possibly in their present.

I know of the old trailer where Stella and Noctis meet - with Noctis in a suit. It is possible that for a while she called herself Luna and even had that necklace. That is just pure speculation, however.

By the way, the two front page pictures both totally look like her. That is she redesigned already. And a way older version (a few years ago) looked a bit more different. So the new picture from last year is the one Edge7 used for comparison and that was the one people used to notice a resign first. And I personally can totally see her in the new trailer just a bit more "styled". I also do not look the same all the time. The trailer version is probablly even ingame (which would be wow) and that is a difference as well. Graphics might also have been polished.

What is sure is that she got that redesign from one year ago. And when it comes to the new trailer I cannot see any more difference than my face has in certain situations. Notice that even I mentioned a slight difference on page 1 and that they could have been siblings. But for me this seems more something of having make up or whatever makes the same face look a bit different. When I remembered that they redesigned her and saw her and not to mention the front hair and all it all made sense. Another revelation would cause confusion for sure. That new picture is even known as Stella by people now.