Well, I'm living proof that you can have radiation a second time and to the exact same side and even the same place after surgery for a recurrence even if you had the "maximum". So it shouldn't even be an issue if it's going to a different side and location.
If they do decide to do radiation a second time, don't be worried by the high GY dosage numbers in the OCF news report. Those guidelines dealt with the situation where surgery for the recurrence was not an option. So the 50 to 60 GY makes sense. In my case, I only needed 25 GY the second time around (compared to 70GY the first time) So your Mom's doctors might use a similar smaller dose the second time.
Charm