"Avengers: Age Of Ultron" has been the most dissected movie even before it was shown (though Batman Vs Superman would challenge). Despite all the attention and scrutiny, there are still some details left secret.

One of them is the role of Claudia Kim. Despite all the details that have already been determined, anything left blank will be filled in by the fans and the internet sleuths. For Claudia Kim, this is what we know (from Screenslam via Comic Book Movie):

"I am a doctor/scientist who is friends with Tony Stark (Robert Downey Jr). But I can't give you more information; my lips are sealed for now. It's very secretive,"

The statement quoted from AllKpop in Korea was: "Soo Hyun has been ultimately cast as a supporting actress among the minor characters of Avengers 2."
Comic Book Movie has identified her as: "Su Yin, the neurosurgeon who tried to correct Stark's deteriorating nervous system in the comics. Perhaps there's a subplot in The Avengers sequel that involves repercussions of the playboy billionaire having shrapnel removed from his chest in Iron Man 3."

What Culture has other ideas: "Some people believe that she could be the latest addition to the Marvel Cinematic Universe's Avengers roster - Ms. Marvel.
Jocasta is an outright robot and therefore couldn't have originated as 'a doctor/scientist and friend of Tony Stark'but if Jocasta's origins are changed and she is presented in the Marvel Cinematic Universe as more of a cyborg or a robot with an implanted consciousness, Kim could be the actress portraying her.

Imagine, if you will, that Kim's character turns out to be an old flame who Tony Stark still cares for. It would add more emotion to the story if Ultron was to take her and use her as the basis for a companion of his own." That would be following the Ultron origin but it's the Tony Stark Version, not Hank Pym.

First of all, if she's just a surgeon, why would she be at the premiere of 'Captain America: The Winter Soldier' and second, what was all the secrecy about?  Perhaps this tweet by Latino Post prime sleuth El Mayimbe could explain:

(Ms Marvel is also called Captain Marvel but there were other characters taking that name)

We will find out on May 1, 2015 when "Avengers: Age of Ultron will finally be unleashed to the world.