Avira, it is true that Chofetz Chaim was talking to those who will listen to him and who were to at least some degree observant. But, there was no strict separation. For example, he writes that it is wrong to fathers to be observant themselves, while their wives and children break shabbos, read anti-religious papers and books, attend anti-religious schools. That is what was “frum society” in Poland in the 20s. It was under attack. He lists, by name, many organizations that he supports, and many, by name, that he is against. The fault in the organizations he objects to are wholesale rejection of Yiddishkeit, focusing on Jewish stories that omit religious content.
We also all know that Ch Ch endorsed Bais Yaakov. Despite that, I could not find any letters that advocate any organized education for women. He addresses the women directly several times – in letters and speeches in front of women conventions. He suggests women to organize to support chadarim, suggest for women who know how to read to teach those who do not know – specifically halochos niddah. In one letter, he summarizes all these laws in a couple of pages to help in that. I do not see him suggesting ways to teach those illiterate women how to read.