I figure our ingenue is about 6 months in to her cross-gender exploration when Daddy's month started. I actually checked hair growth, which is about .5" (1.25 cm) a month, but males grow it slightly faster. That puts Erin's natural hair growth at shoulder length, which I fudged a bit because of available hair models. So, yeah... I'm nerdy like that to try to keep things plausible. (ps: she's using hair removal creme to keep stubble away.)
That said, this chapter will feature a few different styles, so I hope you all will forgive the inconsistencies. Still debating whether to grow it more or cut it short and pixie, like Erin's sister. I can see both working, especially for androgyny.