Michelle Trachtenberg

H&M's Jimmy Choo VIP preview sale on Friday night was a mad scene. Lines at the 5th Avenue flagship snaked around the block to get in (even if you were on the list) and once inside, there was a mini-line to get into the shoe section. In the thick of it all, shoes tumbled out of boxes, tissue paper was tossed and sequins were hoarded. The H&M staff did what they could to restock the sapphire blue boxes ("More size eights are coming up!") and keep the peace among a very determined crowd. Ladies, and a smattering of patient men, were decorous and polite but everyone had an agenda: getting their mitts on some shoes, by any means necessary. Speakeasy scored by strategically prowling for discarded size sevens in the middle of the room.

In a quiet, relatively empty corner of the third floor, we found "Gossip Girl's" star bad girl, Michelle Trachtenberg, shopping with her girlfriends. We pounced at a chance to chat, and she kindly indulged us.

WSJ: What can you tell us about your role in the new NBC medical drama "Mercy"?

Michelle Trachtenberg: I play nurse Chloe Payne. She's a new fish in the pond. She just got a nursing degree. She's fresh out of school and is trying to live every moment to its fullest, and experience everything without killing anyone. She's got a great heart, a really kind soul. She's just trying to fit in with the other two ladies at the hospital.

Audiences watch medical dramas because they know they are going to be emotionally-wrenching. What do you get out of playing these difficult roles?

You definitely want to honor the medical field, that's first and foremost. There's men and women every day that save lives. I'm honored just to be a part of that whole field.

Roles are always challenging because you want to keep the emotion as realistic as possible. I think that's a challenge with any role, toeing the line between fiction and reality. We try to make it as realistic as possible.

Speaking of realism, what kind of medical training did you go through?

We only do on the moment training, so we'll have medical experts on set that are going through the motions. To do a mini-nursing school- you'll forget a lot of the things half the time. So we have the experts on set that are taking us through the motions, making sure that we know what we're doing.

Chloe sounds like such a good girl, while Georgina Sparks is the bad girl we all love. How different are they?

It's an obvious answer. It's night and day. Both characters are great. It's a lot more fun to play the bad girl but it's really challenging and great to play the emotional side of Chloe.

Are we going to see more of Georgina?

Of course.

This season?

(She smiles.) Maybe.