Even if you are the most talented photographer providing the very best customer service possible, you will at some point in your business have to deal with an unhappy client. It happens to us all. We can't please everyone, and at some point we will probably drop the ball and not deliver our best work or best service.
So what do we do when we have a client who is unhappy?
1. Pick up the Phone
Call the client rather than email. This will show them how important they are to you and how serious you take their complaint. Additionally, a client is much more likely to be calm and understanding if they are listening to your sympathetic voice rather than reading a dispassionate email.
2. Stay Calm
Do your very best to keep your cool. If you are already feeling upset or emotional, wait a day to call. Email right away, and ask her the best time for you to call the next day, so that you have a day to try to calm yourself. When you do speak with her, no matter what she says, try not to get defensive. This will only make matters worse. Try to be sympathetic and see things from her perspective.
Find out why she is unhappy, then apologize, whether you think she's wrong or not. This is Customer Service 101: the customer is always right. Repeat back to her what you heard and offer your apology. "I understand that I didn't capture the sibling photos you had expected to receive from your session and I am terribly sorry. I can see how disappointed you are."
4. Have The Client Suggest a Resolution
Ask her how she thinks you can resolve the issue together. She might already have something in mind, and it might be simpler than what you would expect. Keep in mind you don't have to give her what she is asking for. If her solution is unrelated to the problem, it won't be helpful. A free Wall Portrait will not be an appropriate solution for missed shots.
5. Offer A Resolution
After you've heard what she would like, you can offer what you feel is an appropriate solution based on the situation and what she wants. In some cases it might be a free print, a reshoot, an extra mini session to capture shots that you missed. Or if you feel that this work was up to your standards and you don't believe you could do anything better to make them happy, I would just offer a refund of their session fee and offer to refer them to another photographer that would be a better fit for them. Do your very best to make the client happy without compromising yourself or your business policies. But remember that it's better and often easier to make a client happy than to deal with bad reviews.
6. Do Better Next Time
Once this issue is resolved take some time to look at what went wrong, and how you can prevent this problem in the future. I have found that most issues come from a lack of communication. Are you sure you fully educated your client. Could a new client preparation guide or new studio policy prevent this from happening in the future? Did you know what the client was expecting to get out of their shoot? Would a new client questionnaire or a phone call prior to the session keep this from happening again? Make sure you learn from your mistakes and make your business better by reflecting on them.