Answer by Professional Japanese Teacher
Onna no ko
The word 女(おんな) onna means “female”. To distinguish between an adult and child female, 女(おんな)の人(ひと) onna no hito (female person) is used for a woman; and 女(おんな)の子(こ) onna no ko (female child) is used for a girl.
If you wish to mean your girl as in “daughter”, you can use the word 娘(むすめ) musume. Your colleague’s daughter would not be called musume however.
She would be known as 娘(むすめ)さん musume san. This is the same idea as when we address other people by adding “~san” after their names to indicate politeness.