Some clients don't know much about hair, and don't know how to do proper hair care. While you can try to assist them while they are facing the problem and do your best to resolve it... there's fairly little you can do.

Even when sometimes trying to help someone who possibly doesn't seem how to take care of hair, they might get defensive and say something along the lines of "I'm an expert, I know how to deal with it". At that point they're mostly beyond reason. And there's a chance that they have bad intentions and want to take advantage of you.

Try to deal with it by staying professional, even if it requires you to be tough. But don't be taken advantage of either.