I do think it's serious, OP, and I do think it harms patients. Those slots were supposed to be used by real patients - if a full time doctor did that every week that would be ten patients missing out on an appointment slot and some of those patients would have really serious illnesses whose diagnosis and treatment would be delayed as a result.
In addition, if it was real patients whose medical history was being falsified that could also lead to serious harm down the line if their records suggest that they've already had treatment they didn't have, or haven't had treatment they shouldn't have, or contain false history that means the doctor subsequently treating them doesn't take the right factors into account when deciding on a plan.
This level of dishonesty would normally get someone struck off so I think the GMC must have had some sympathy for her as well as as some confidence that she wouldn't do it again.