If by "the girl" you mean Ther then they are not a girl, it may not be really obvious, but they are referred to as "they" most of the time, both in Glut and Killer Chat.
Their story is romantic BUT it is not the main point of their story to be romance, at least not in the same way as in Killer Chat so comparing the two games plot and topic ways is not necessary.
Also, you said that you can see how Rose's writing got better in Killer Chat, I forgot to reply to that; Killer Chat was written in a month for October Jam while Gluttony Gods is a story that is with Rose for way longer, so I wouldn't speak of improvement when one story is still being heavily progressed and on a complete different topic and vibe than the other.
Though, I'd like to hear what in your opinion is an improvement in the writing, because I'd say that even as someone who started with Killer Chat, I like the writing in Gluttony Gods better.