I strongly suspect that much of Hina Nemoto's personality especially her aspirations to become a voice actress is based directly on Izumi Kiita, Tomoko's voice actress from the anime who is also heavily involved in the yuri manga scene as both a writer and editor, so, yes, any assumptions about Nemoto's sexuality are probably correct.
According to translated interviews I've read, Izumi Kitta keeps in touch with Nico Tanigawa and she sends them plenty of suggestions on things she'd like to see in the manga.