I dunno.. She has been singing like that (sounds flat) since talkin' to myself. She wasn't like that during glitter/fated or even the A BEST 2 era. Personally I dun believe she's struggling or forcing to hit higher notes. It's just that her voice is very very flat lately. Together When... at musicstation is an obvious example. I was like, "what's going on?"
I dunno. She might sounded flat during probly 5 or 10 seconds during a live performance back then, but not like this time. Her voice was so flat for 80% of TW... weird..