Great to see this site back and nice to talk to you all again.
After observed the teasers, Shin Hye does less frowning in some emotional scences; previously she had a deep frown and it might be a distraction for some scenes - it's just my pov. When doing a surprising look, her eyes opened little widely and then narrow down to express a feel "oh...you saved me and what'else?" - which is good for high school day. Hope she show a deep love when in doctor days. It's a good sign for me. In 2 first teasers, she seemed to feel "sad expression" when meet the teacher again. I don't know why I felt like that but look forward to storyline - perhaps answers are there.
When someone bother her, her face is between expressionless and glazed look to say "I don't care and you're annoying." - a little sneer can be added to say "you're really nothing for me." in my opionion.
For love scenes, now they are lively ones, not passionated. I think she can express a deep love, not intimate act.
Oh, I wrote too long, hope you don't mind. It may be too much interpretation for 5 minute teaser.