>>3622001Here's what I think.
As far as anons know, Gura's living alone and away from home for the first time. That's probably why she's sad a lot (especially during Christmas). Kiara's been living alone since she was 15 (not just that, living alone in a foreign country since her teenage years), so she has a bit of life experience and wisdom to give Gura, so naturally she's very protective and caring for her. Clearly she sees herself as a big sister to Gura, and the whole living alone/life experience narrative explains why.