"Bonito" is a masculine adjective meaning "pretty" or "handsome". It's used for both male and female subjects, and its meaning doesn't change based on the gender of the person being described.
For example:
* El niño es bonito. (The boy is pretty.)
* La niña es bonita. (The girl is pretty.)
If you need to emphasize the feminine gender, you could use "hermosa" instead of "bonito", which is a feminine adjective meaning "beautiful".