Well here's another ballad diva from the UK I just recently discovered.
Alexandra Burke
http://www.youtube.com/watch?v=bsuXbkrA_AQ
(This was the only vid that I'm allowed to link to. For some reason her vids are blocked off to Americans.)

Though I don't like Alexanda as much as Leona, or Camellia (Tsubaki)
Still some mighty magnificent pipes though.
Hah judging from the comments. It seems that all three of these girls (Posted in the thread so far.) get hated on for singing covers.
I say who gives a fuck as long as they sing good.

While I'm recommending ballad singers here's another one from Japan, Nadia Gifford.
http://www.youtube.com/watch?v=PnUlbBiDN94
http://www.youtube.com/watch?v=UfHhyiTo9Pg
See the playlist I made to hear more of her ballads.
http://www.youtube.com/view_play_list?p=1E0B0FB1DD57A380

I'm not sure if Nadia is an actual singer though, because the only music I've heard from her is from a fucking video game.
(Steambot Chronicles / Bumpy Trot.)
What's funny is that Nadia happens to be a much better singer than most of the so called music artists in Japan. (Let alone the rest of Asia. Who also make crap.)
Judging from the two ballad divas from Japan that I've posted so far.
It's pretty safe to assume that most real singers in Japan get no love at all.
(Too busy to jamming to Ayumi Hamazaki's latest bullshit. Hell even singers who actually can sing like Mika Nakashima aren't even that great, because that Mika bitch sings with no soul.)