Thanks for the translation!
And I agree - suddenly, Momoko and Mother Ichi were basically life partners from day one until something presumably happened? And while Momoko is tight-lipped, vague, and overall hard to read, Mother never showed any reaction or anything to Momohana/Sumire having Momoko as an elder sister. This whole arc is enjoyable and I'm interested in seeing how it ends up to the present day situation, but their close relationship does seem out of left field.