just more timeline feedback, DD developed breast buds (well it was more just the one side) when she was 8. It was a little surprising, but we noticed that it didn't really grow for a long time and for more than a year it was just the one side slightly swollen.
about age 10-11 more growth started occurring and she then at least had two developing even though they were (and are) still different sizes.
now that she's just turning 12 and I've noticed that she has been developing much more and is moving more to the rounded breast and away from the pointy ones. the inconsistency in size is still obvious to me, but I may be paying more attention because I've always been a bit self conscious about the fact that my breasts are obviously different sizes (which is perfectly normal but another physical feature to nitpick about).
I thought that 8 was very young but was happy that nothing really happened for a couple years after their first appearance. now that shes 12, i'm now waiting for menses to start.