So, in the credits of BBS, there is this scene where Kairi is picking up flowers and then turns back and stares at something in the sky as her little pendant glistens. What's up with that? I really don't get what it means. Someone care to explain to me?

i think she sensed that something was wrong with aqua

yeah i think it was probably when aqua fell into the realm of darkness

I assumed it was when Xehanort kidnapped her to send to the ocean of other worlds.

from kingdomhearts.wikia.com

 

After Xehanort's defeat, Kairi is seen picking flowers in a large garden. She looks up to the bright sky, looking as if she sensed something. As she does, her necklace emits a weak glow

 

It's probably either that she could sense that something bad happened to Aqua or that Radiant Garden is going to fall to darkness.