Aziza is a sponge. Like most kids, she soaks up the influence of her environment. The only catch is that she doesn't discriminate—she soaks up the good and the bad alike. That can be a dangerous thing in a place like Afghanistan, where there's a lot of bad.
Aziza imitates adults frequently. After Zalmai is born, Laila notices how Aziza develops a "queerly adult headshake" when she plays with her brother (3.40.28). Likewise, when she's finally reunited with her biological father, Tariq, Laila is again amazed how quickly she is "finishing his sentences and he hers" (4.48.15).
There is also, of course, the bad. This can be seen most notably when Aziza is sent to live in the orphanage. Laila can see a marked difference in Aziza's personality. Aziza acts shameful about her squalid living conditions, and she's even started developing a stutter.
These dramatic shifts in Aziza show us how dramatic and dangerous conditions for children—especially girls—can be in Afghan society. Aziza hasn't had it easy—that's for sure. We can only hope that she, like her mother, learns to use the difficult experience as motivation to do better. After all, being a sponge is a great gift. Aziza should be thankful that she has parents like Laila and Tariq to keep her soaking in the right stuff.