@narra Most likely when Senshi went to draw water he saw "something" moving in the water, stuck his face in to take a better look, and immediately got jumped by the Succubus larva.
I wouldn't jump to conclusions. I think she's just a romance novel fanatic and is naturally curious about such things. Like how she pried about Chilchak's situation or why she was able to conjecture so well despite obviously not having romantic experience, having dedicated her whole life to research. This also explains why her "perfect man" was something right off of the cover of a woman's romance novel.