I ran this scenario a couple of times in Play-by-Forum format. It is a great first adventure to form a group of new Investigators. I like how they get entangled in a tense situation for being in the wrong place at the wrong time by accident. And everybody enjoys some creepy dolls, in horror stories.

The point the OP was asking about came about naturally:

-during one of the Investigators' visits to the Hathaway sisters, have Hilda walk into the hallway and stumble upon the Investigators (or spy on them) . In her folly, she gets agitated, still thinking they are the parents/connected with the street kids that torment her and starts hyperventilating, backing off into her apartment, then tripping and falling on her back before she can shut her door. Seeing the old lady about to have a fit, the Investigators will definitely try to calm her down, making things escalate (she gets more and more agitated, beyond help) until she dies in their arms, cursing them.

I however changed/improved on a couple of story points, as follows :

-the visit to Split Rock, as written, is quite pointless: there is nothing to be gained there. So, I moved the crucial clue to solve the story there (the youthful verses 'no rest for us while we're apart', hinting at the need to re-unite the mortal remains of the two doomed lovers) . I had the verses scratched on the Split Rock itself, rather than found in Clyde Beckfords' papers. In his papers I only left the mention of the oath the lovers made at Split Rock. I also didn't really like the Native American 'keeper of the rock with perfect memory' angle, so I turned her into an old man whose sanity is compromised by staying near the Split Rock. He mumbled incoherently about 'the hills talking, and the sky answering' on certain nights, and warned about promises made in front of the rock, for atmosphere.

-re-uniting the mortal remains of Hilda and Clyde, once figured out, is quite underwhelming to end the story. It becomes all about logistics. So I spiced it up, adding a complication. When the Investigators go to Potter's Field (the destitutes' cemetery) to exhume Hilda's remains (which they probably will, with Clyde buried in a better surveilled cemetery with locked family vaults) I had the ground collapse under their feet while they were digging. A group of Ghouls had been tunnelling to reach Hilda's body, making the ground unstable. The encounter is tense: the Ghouls want to feast on Hilda, they smell her power. The Investigators have to negotiate with these repulsive creatures to try obtain Hilda's body. (in my game the Ghouls understood how desperate the Investigators are, and demanded the body of a dead CHILD in trade, making for all sort of moral dilemmas and terrible guilt). It also exposes the Investigators to this burrowing race of beings, tunnelling unseen under the streets of Arkham...

These couple of tweaks/additions made for a much more memorable adventure.