Btw, I went back to check just to be sure
Consider this just a theory, but I am pretty sure about this:
First of all, it's true that the "six months timeskip" is a top bullshit move to skip character growth/development, that is facts.
Now, for the theory, I'm pretty sure, judging from her uniform, that these 6 months are still hs times. She's wearing a short-sleeve shirt, meaning she should be wearing the summer uniform, meaning they're in the first half of the year. So I'm pretty confused at some people writing about trains and universities....
Now, we also have to consider that we lack context: if my previous theory is correct, it's impossible for them to not physically see each other, as they are classmates. If they didn't see each other, it would mean that she dropped out or changed school.....that's a bit unrealistic.
So, I think that for 6 months, they either didn't interact much or they didn't "see" each other (as in "fanbox style"), she could have started going to a cram school so the time to be together reduced or something, she could be "un-gyaruing" herself to become a proper teacher....we'll only know in the next chapter