Yeah, I'm not exactly big on the whole length thing either, if there's a conversation going on and it's very back-and-forth, then just let the posts be as long as they need to be, I say. Don't force lengthy posts into a place where things should be fast-paced both in writing and reading. Or in this instance, it's simply a small conversation, not every post needs to be a profound exposition into a characters soul, putting that much navel-gazing into one spot makes for a very heavy over-expository beginning making it so that characters really don't have anything left to be revealed about them by the time the story gets a-moving.

There is a counterpoint in saying it helps to establish a character well early on to have them clearly defined in the beginning, however, I think for a world that we don't really know that much about, at least as far as its myths, history, lore, and such go, it's perfectly acceptable for a character to be very heavily archetypal and develop over time into something else.

I'm trying but there's not much for me to post to.

That is actually never true. Just because people aren't saying much at all doesn't mean you can't describe your character moving around, hand gestures, facial expressions, their thoughts, etc. There are a million things you can have your character do in a single post. To demonstrate I'll do that right now.

You don't see any of the other female characters going "RAARGH I"M STRAIGHT, I"MMA HUMP EVERY GUY I SEE!"