Christine gave you a great answer. Knowing your client’s goals it would be make it easier to set a time frame to achieve them as long as they are not unrealistic. Sometimes losing the weight or going down dress sizes might not be enough to satisfy a client. This could be because of other factors the client is dealing with and have nothing to do with fitness or dress sizes. This type of client is hard to make him/her happy because they will never see themselves as a “success”. You can have a deeper conversation with her if you are comfortable doing so and maybe you could get a better idea of what the real issue is. Quick fixes are not a solution to any problem because they don’t last.
What was her starting point (aerobically, strength, overall fitness level, BF%, weight, etc.)? If all of these have improved then she is on the right track.