"I believe that you should not use the "G" because it doesn't technically meet the definition"

There is a G code for the 1099-R. There might also be a G as a Program Code for the form you are working on. Let's not treat these as the same purpose or function.

"called indirect rollovers"

Yes, and you also need to handle if that is Gross or Net.

"took her RMD early in the year and then wrote a check to return it in July."

Because any withholding that was not "made up" as part of the re-deposit means there is a Taxable Distribution still with the Feds = as withholding, and the total was Not rolled over.