good girl

Short definition from Wiktionary

Noun

1. 1
   An obedient female dog, child, or someone who behaves like one, even when deemed inappropriate.
2. 2
   A demeaning term of address to a female.

Interjection

1. 1
   Well done, to a female.
2. 2
   Said as praise to an obedient female dog or other female domesticated animal; see also who's a good girl.