Most does don't show until their last month, but it will mostly depend on the doe each one is different. Most of my does are 8 weeks from kidding an some have bellies an some don't. So like I said just depends on the doe. You got a picture of her?
The belly doesn't show as much as the bag and vulva. I have purchased goats that didn't look bred at in the belly but spit kids out a month later. At about 3 months bred she should start to form a bag...udder what ever the right word is for goats then as time goes on it will fill out more and her vulva will start to get loose.