When do you stop calling a female a girl and start calling her a woman?

Anonymous
I’m in my 30’s and I am seeing this female who is in her 30’s too. I feel weird when I refer to her as a girl. For example, if I say, “I’ve been talking to this girl for...”. Or, “this girl I’m seeing...”.
When do you stop calling a female a girl and start calling her a woman?
7 Opinion