Not bad, this far... but...
I was awkward and nervous as a 14, 15, 16, and 17-year-old (not to mention 9, 10, 11, 12, and 13!), so I get the nervousness issues and such...
But I don't believe I've ever failed to complete a sentence, unless it was intentional, and I've never, EVER, had my thoughts stop me with some kind of "I can't say it" kinda thing. It's not like they're making a deep love confession to somebody they met 7 minutes ago; they're just saying they think the person is neat, or that they like their company.
I mean... no need to lose your fucking mind over it, right? (Unless you have such severe and deep-seated trauma that you are unable to communicate with any other humans on the planet... but we didn't start with the character claiming to be severely autistic, or unable to use spoken language for communication, now did we?).
(See? Totally unable to NOT complete a sentence!)
And while I know my experience isn't universal, this level of social awkward seems so unrealistic as to be difficult to read.