The attack happened on the 900 block of East Myrtle Avenue at about 12:30 a.m.
The girl was with her 10-year-old and 1-year-old brothers.
Two pit bulls lived at the home.
Glendora Police say officers shot the dog that attacked the girl, but the dog still ran away. The dog was killed when another officer ran the animal over with his car, fearing it was a threat to others.
The girl is expected to be OK.
The second pit bull was taken away by Animal Services.