Now that the comics are all done, I'm a bit surprised how Furth/David/King never bothered to follow up on Rhea (unless I missed something) and what happened to her.
Given that Roland effectively hinted that he did encounter her again and killed her, it would have made sense for him to encounter her at some point before the events of the Gunslinger yet Furth went from the events of Wizard and Glass all the way to the end of the first book and she never appeared.
Granted given how King effectively wiped out the comics from continuity with his last DT novel (or as Furth said, relegated them to "another level of the Tower"), I guess it would just be a "what if" but still...