All in all, if the situations didn't seem so fabricated I might've found them funnier. As it seems we're not laughing "with" the main character but "at" her. And honestly I don't know what I really feel about it. Then again, I might simply be overthinking things, but there's still this nagging feeling of "Why in the world are you doing this?" that I can't shake of no matter how I try.
Well, vol2's omake kind of explain things a bit more : Shinozaki is not that socially capable, she thinks there are rules to being social and that following those rules are the only way to have a successful and socially fulfilled high school life. Hence why she was so sure that missing out the first week of school would destroy her chances to make friends.
Shizonaki seems to be actually socially awkward, which is why she goes out of her way to make friends and get confused a lot when things don't go as she expected. I find that quite interesting and that she always have such over the top reaction make it even more funny.
And yeah, think you're overthinking things a bit too much. I love mangas, but I don't think there's a deep meaning for most of them. Most of the time, it seems to me that it's not much beyond "hey, this is fun, let's make a funny story out of it !", especially when it come to slice of life.