User blog comment:FinalWholockianGrrlGamer/Headcanon: Summer Rose/@comment-71.236.149.108-20140110012905

One of my friends has pointed out that being happy and cheerful is a real way to deal with the death of someone close/important to you. So, the trailer could have been in the past, rendering your theory completely worthless. If Ruby's cheerfulness is a way to cope with Summer's/White Cloak's death, and Yang is being clingy because she doesn't want to lose Ruby too, it can make as much sense as your idea.

However, this is just my personal idea, and has no real (in show) evidence, just some ideas.