The sentence before that sentence is “she's called that because she is the caretaker of the catacomplex's lifers. Adult nymphs often drop their epitaphs in favor of titles.” Using the context provided by the previous sentence, I think it’s clear that that sentence is in reference to her. If you think about it, it wouldnt make sense to drop a random fact about adult nymphs if no adults are present to remind Ly’lac of that cultural fact, yknow?