Answer:
If you take a picture of someone and without their consent publish it and/or make money from the photo technically yes. You need to have them sign a model release form. If the picture is in any way compromising and results in an unpleasant situation for the woman, she can "sue" you in civil court for a number of things.
Depends on where you were:
In a bathroom or locker room where there is an expectation of privacy (a reasonable belief that you're alone), then YES.
In public, on the street, restaurant, beach, park, etc. , then NO.