⟩ As you know sometimes we get involved with a client and have to stay later than scheduled. Would that be a problem for you?
There are limits to the questions that can be legally asked in a job interview. An interviewer can't ask you how many kids you have, if you have a car or any other personal questions. But that doesn't mean you should try to hide pertinent information because it will only backfire on you down the road.
You are building a relationship with a manager that you hope to work for. Don't start your beauty career off on the wrong foot. Tell her what she needs to know for the good of the salon.