Maud de St. Hilaire - Death

Don't know them, but medically, they could easily have caught the same fatal disease, romantically they could have died of broken heart or some Romeo/juliet scenario, or criminally, may have both been murdered, or hanged even. My guess is the first, based on the times.

There's also the possibility of Dumb Researcher Error - somebody slapping the same undocumented death date on both of them because reasons. Believe me, I've seen this.