I have extended my hours in the past due to being desperate for clients, and I have sorely regretted it. I am finally getting rid of this family, and I am seriously dancing for joy that I get to close at 5:30 now. It went against my better judgement, and I totally DID end up resenting them.

DON'T DO IT. You'll get clients who respect your operating hours.

Tell her that while you appreciate that some people have a long commute, you have found in the past that it greatly affects your family when you operate outside your business hours, and unfortunately, you have to think of your own family as well.

Good luck, and don't back down!