Of course, the “girls” are really women. I think it's fiction about women we’re talking about as a “trend.” Women as protagonists in non-romance fiction is becoming a big thing. Goodreads’ Listopia has a list of 749 books with “Girl” in the title! This trend doesn't show any more signs of stopping than books with “Vampire” in the title.
So what is it about literary trends? They say you shouldn’t write to them because by the time you finish your book, the trend will be dead. They’re actually speaking of agents’ and editors’ ideas about trends, not actual trends in real life or even among readers. I think trends ARE something you should write to, if you feel them and care about them. It’s something you can do beyond voting. It’s a way of speaking up that matters.
I think the "girl" "wife" trend reflects a big shift underway in our culture -- a mega-trend, if you will, and one I think those of us who want to should chase. It's a re-visioning of what it means to be a woman, and WF is a fantastic medium for exploring these cultural shifts, especially as they pertain to being a young woman in a rapidly changing culture speeded up by technology.
I'm not a young woman, but I like writing about them. I like exploring the way women find themselves, and create or recreate their lives. I'm a rocket scientist's daughter, so I'm fascinated by the impact of technology on cultural shifts and the way women are perceived in the world. These two trends power my fiction and my poetry. I guess growing up in the 60s, when women's roles shifted dramatically, especially in the workplace, has given me a lifelong interest in trends. So I write to the mega-trends and could care less about literary ones.