Imagine killing one of the main, beloved characters near the beginning of a chapter, then not touching upon that for the remainder of that chapter, only to make people wait one more month, at minimum to see the aftermath, assuming the story doesn't focus on other stuff.
The part that irritates me the most is it's been so many months since we last saw Hiyori, and when we finally do we get this shit and gotta wait longer.
I imagine she'll be fine. Whether she becomes someone equivalent to Yato's dad, or by some other means gets brought back. I'm pretty sure it's never been explicitly stated that it's impossible for humans to be brought back in this series. Her body is still in tact and in good shape, so perhaps if she could be returned to her body there's a way for her to be alright. One thing I'm kind of expecting is the goddess Amaterasu to get involved, and perhaps be the one to save Hiyori. Amaterasu has been shown to involve herself with the characters before, such as Yato's adventure to the underworld, with her randomly appearing and telling Hiyori and the others how they can save Yato.