Hmm... thats a good challenge for drama addicts :D
I remmember that there was j-drama with Maki. Her family was murdered and it was beleived, that her brother killed them. Then she moved somewhere else, but she was really sad and closed herself from the world. But then she fell in love. I dont really remmember, if it had good or bad ending :-/ It was called Innocent Love
Then there is Monstar - new drama, where the female lead isnt very "happy-go-lucky" character. She is also a little bit quiet - but strong and interesting. I really like her as a character.
I saw in your PTW list Thorn Birds - the heroine here is also like this, because she went through a lot. She is very outgoing in the beginning, but after some time, she becomes more reserved towrd others.
Ahww... AND you didnt watch Cinderella Sister!? The main girl here is REALLY amazing. She is also very intresting character, who is rserved and closed herself before others. God... I love that girl :D She is my favourite character of all times :D
And here are some others: Chilling romance (absolutely adorable movie also with a quiet heroine), Hear Me (tw-movie - also very cute and romantic), missing you, Nobuta wo produce (very good J-drama), Thank You (older k-drama), that Winter the Wind Blows