Hey :)

She said that at Strong Heart Episode 11 (091215)
You can watch it on ssf : CLICK HERE 
Sorry I can’t find a youtube vid for it.

But here is Taeyeon’s explanation about it on Chinchin:
CLICK HERE 

Ohh yeah. I’ve been thinking about that too. And it seems that there’s a lot of you that didn’t know some of the moments I’ve been posting. Okay. I’ll post links from now on :)

Thank you for suggesting ^-^