Although goats "bag up" differently it looks to me like she is still a ways off from kidding. Could you possibly be a cycle off on your dates? As for the uneveness it is hard to make out in the picture just how unbalanced the two sides are. Is this her first pregnancy?
Sometimes goats are just a little unequal, however, some things that can cause unequal development are previous mastitis, extra mammary structures such as duplicate duct system (these may or may not have extra teats associated with them), tumors, teat sucking- either by herself or another animal at the barn. There are other things as well. http://www.goatwisdom.com/udder_care.html
The main concern is developing mastitis or having a lot of scar tissue from it. At the least watch and check for warmth, discomfort and redness. Try to not handle her udder too much or too firmly, you don't want to stimulate milk production. If you have a vet or an experienced goat person that can take a better look they can give you a better evaluation.