As I always remind myself when new chapter arrives, it's worth the wait.
Letter drama should straighten the Hajime character, even if with not so positive things.
Hajime overall is a really strong character, she holds a burden, that destroys her whole view of the reality, but still finds reasons to continue. Even though we might say she's running away from facing it directly. Regardless, just the fact, that she didn't break says a lot.
You might say, that she made up an illusion, where she must ensure Momoka's happiness without considering her own well being, but she could've just thrown it all away. She could be seen as someone, who lost hope in life, but I think there are feelings deep within that someday she might be truly happy.
If letter moves plot a way I assume, we should have something like Momoka's breakdown, Hajime's feelings revealed and hopefully her leaving Kyou's shadow to walk her own path, whether with or without Momoka.
Them getting together sounds positive and all that, but it seems extremely complicated. Lets just hope author either makes it thoughtfully and without obvious inconsistenties, or leaves it in some other, maybe kinda dramatic state.