Was Kyoko and Chizuru's first meeting ever shown in the manga?
Yes, this was shown in Chapter 35 of volume 4 of the original Japanese manga. The anime adaption only made minor changes, such as the place of their meeting is changed from the school library to a local public library, and Yui's Kanji exercise book is seen with different contents.

You can refer to this page for detailed information. I personally find this "Yuru Yuri database" site very useful in answering questions like yours, so please allow me to recommend it to any of the Yuru Yuri fans here.

Also, since a long time has passed after this question is first asked, it is highly possible that amateur English translations are out there right now. Maybe I should not provide a link for copyright reasons, but googling will certainly lead you to one.