There have been since early times female anchorites and hermits, some associated with monasteries and some not. “Nuns” (not to be confused with “Sisters”) are basically female monks. It would be interesting to know if there was a convent of female monastics at this location and if this particular woman was a nun who had been “mis-gendered” by earlier researchers. There’s a lot of details not included in this story that could shed light on that.
Nuns and sisters?? Two names for female monestics. The same thing.