This is my perception of how Tenten really is (at least in the episodes)...
Disclaimer: If I owned Naruto, Tenten would have a surname ... one that starts with H. (I don't, never have, and most likely never will own Naruto)
Tenten's Quieter Side
Tenten isn't naturally loud. She doesn't like making things noisy and she doesn't like it when people around her are noisy (Uzumaki Naruto isn't one of her favorite people). She likes quiet and she likes quiet people. She doesn't mind speaking quietly- she does it all the time- just speaking loudly.
Oh, of course, when she sleeps over at Sakura's or Ino's house she makes herself loud, noisy, noticeable, because she doesn't want to be forgotten. But she doesn't like it, and she feels uncomfortable. She lives in a world where noisy people surround her, but she deals with it.
Some days, though, she can't deal with it. Tenten has always felt bad for Sakura- her teammate left her, after all- but as Sakura kept chatting on, and on, and on, and on, she found herself loosing all her sympathy and thinking 'no wonder Sasuke left; her chatting is enough to drive anyone insane'. And then she felt bad- she felt really bad, because she knew that wasn't true, and Sakura was just trying to be friendly. She ended up asking Sakura if she wanted to go get a muffin or something.
People assume that Tenten spends so much time with Neji (outside of training) because she's infatuated with him. They also assume that she is quiet around him because she's too tongue-tied to speak. They aren't wrong- but they aren't right, either. She is infatuated with him, (although she thinks it might be something more) but she has never been tongue-tied around him. She doesn't speak around him because she doesn't feel like she needs to- she feels like she can be her own, quiet self around him, and he'll understand.
End
(And no, I will not make a sequel because a one-shot is supposed to be just that: a one-shot.)
Hugs:)
Tiramisu122