I also got both my females at 10wk. They were a lot bigger than I thought they'd be at that age. Like I said, at 10-12 week, they are roughly adult sized, they just chub out a little more rather than get physically bigger.
She's only 5month now, so it's only been a few weeks. Mine aren't much bigger now (at 14month) than they were when I got them. Females are often smaller. I wouldn't worry at all x