Kara's whole purpose and storyline is about teen angst. You couldnt have a show about her and not have it be about that. However...
The casting seems terrible. Starting with Kara, she looks older than she should be and the trailer makes her seem like the nerdy persona of Clark, when she should be the normal teen blonde bombshell. Seems like they're making it the generic story of an unlikely, unpopular, awkward character becoming a superhero thats been done a million times when that shouldnt be the case with Supergirl.
Then there's Jimmy Olsen... They made him a black guy. Thats another of the most widely recognisable red heads in the DC universe made into a black guy. They did the same thing with Wally West/Kid Flash in the new 52 Flash comics and while I can absolutely understand why DC needs more diversity and the show needed to find it somewhere, I absolutely hate this trend of turning established characters another race because there is absolutely no reason whatsoever that they cant make a new character who is just as good thats a black guy. And not only is this version of Jimmy Olsen a black guy, but look at him - he doesnt resemble the character even slightly. He's a decent looking, in shape guy who is going to wear trendy stuff. So tell me again why they couldnt make a new character? Just look at the success of Diggle in Arrow. DC comics liked him so much they added him to the canon comic. Call him Ommy Jilsen or something, dont pretend he is something he isnt.
The action seems decent enough but from watching that trailer I expect I'll probably skip through the rest because it looks a poor effort.