1. Shane recognizes the woman with the cane and is happy to see her.
2. In chapter 84 on the way back from the Zuytzorp Cliffs Trevor asked Shane "Are you sure we’re going the right way?” To which Shane re[lied “Kinda. Mr. Blake hates the hike and Mrs. Blake can’t do it, so I’ve taken charter guests to the cliffs before."
3. In the prologue, 'Rachel remembering her young son saying goodbye to her that morning, and asking her to bring him home a seashell for his birthday.' In chapter 98 the woman approaching the boat is carrying an enormous conch shell.
So, from 1. above Shane recognizes her and is happy to see her and from 2 above Mrs Blake is somewhat disabled. Conclusion: The woman is Mrs Blake and from the last paragraph of chapter 98 the woman is Trevor's mother, Rachel.