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小妞儿， 小妹儿，猫女士 (okay this one's ridiculous but I find it kinda funny)... If she's called Little Lady because she's a bit sassy, perhaps 小公主？

妞妞 或者猫子。

小黑

I recommend she can called 乐乐 布丁

How about小可爱 ?which means cute baby.

How about 小猫 ？