Not that long by the look of her, could be tomorrow, could be a few days. But this is a guestimate, because it can be really hard to tell sometimes. I don't recommend keeping her in a breeder box though, those stress them out, and stress is not good in labour for any animal. Better to let her birth in the main tank, provide plenty of plant for the fry to hide, then scoop the fry into the breeder box to raise them for 2-3 weeks in there, then put them back into main tank. Or transfer them straight to a grow out tank.