It's very different to write an introverted character - especially a female one. Nathan was introverted, but - let's be honest - most men don't have half of the crap going through their heads that we do. And Stella wasn't giving him much leeway to keep things inside, anyway.
I absolutely love introverted people (Hell, I married one). And, if you're socially awkward, too? Well, that's just icing on the cake. But, damn, it's hard to get inside of those brains sometimes. And the whole thinking-before-they-speak and vigilantly-calculating-decisions-way-in-advance processes are very foreign to me. And don't get me started on needing quiet and space to think through things...
But I'm going to do my girl justice. Or lose my mind trying.