I'd like to start by saying I can't explain her speech pattern in Japanese. I've only read the English version, so I have no idea how she actually speaks, what accent, or any other details about her speech regarding Japanese culture. There are a few different Japanese stereotypes she could be, but I'm not even going to try and guess.
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I know she isn't really a perfect example of this, but her speech pattern is similar to a gaudy, stereotypical "valley girl".
I don't know if you've ever seen the movie, but Legally Blonde is a good example of her speech pattern. If you can, watching that movie might explain a bit.
I'm not sure about the original Japanese speech pattern, but in America, that particular speech pattern is associated with being an airhead or being scatterbrained. People with that speech pattern are usually fashion obsessed and care more about outward appearances than inward ones. The slang we typically call people like that is "shallow".
However, some people may talk like that out of habit or to make them
appear like what I mentioned. Like in the movie I mentioned, the main character, while having that speech pattern was actually very intelligent. So people with that speech pattern
can be smart, but are usually portrayed as being ditzy.
Here's a typical
example of what people usually view a valley girl to be like.
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I was debating with myself whether or not to mention another possible speech pattern, but I guess I might as well as to give you a more complete understanding.
There's another group that is known for saying "like" a lot. That is the "surfer" and "skater" crowd. The speech pattern is associated with people who surf and skate as a sport. Often, people view them as unintelligent (even more so than the last group) and foolish. The main distinction is that they typically say "dude" and "rad" a lot (at least, stereotypically).
Here's an
example of what many people view surfers to be like.
I hope that helped! If you need me to, I can simplify or expand upon any explanation I just gave.