Well... to be honest, the character comes across to me, rather strongly, as a Mary Sue. Now don't get me wrong, I'm not one of those rabid anti-Sue haters - I'm very forgiving indeed - but this really does sound strongly Mary Sue. She's not just an artist and writer, but an EXCEPTIONAL artist and writer, combined with "faults" that, to be honest, are pretty common to many teenagers of that age, so I don't see her flaws as being of any significance. I'm a strong believer in real flaws in characters, because they prevent them from seeming two-dimensional and just an extension of ourselves. And they also make the characters come across as more real and can gain the reader's sympathies better. So maybe if you could find ways to flesh her out a little more, I'm sure she'd be great.
