First, you are referring to informal situations. But, this is (supposed to be) a professional setting, and the rules are much different in a professional setting. Generally, you want to refer to the femininity of women as little as possible in a professional setting, and when you do have to refer to their femininity, you must be extra formal.
Here is the rule I go by: never call a woman a girl in a situation where it would be inappropriate to call her a bitch (she better be a good friend). And, never call a black man a boy because it is almost as bad as "nigger."
If you don't understand the reasoning behind these rules then you should find a good friend to explain them to you very carefully.
