My theory: if the Losties in the past are actually in the FST, then Hurley's notebook with The Empire Strikes Back could have been leaked to Pierre Chang with the help or Richard (and maybe Jacob, who knows), creating a different (better by Hurley) movie if George Lucas saw it. This could have made Star Wars fans who saw the movie in the FST have flashes about the original in the OT, and trying to find why they have those flashes would eventually take them to the Island. But since they can't go to the Island because its submerged, they would have to Travel backwards in time to the XIX century (where they could be sure the Island existed), to find Jacob.
Perhaps the FST version of that woman was one of the fans, and by going to XIX century island she was found by MIB, who killed Isabella and used her image to fool Richard and give him Eyeliner (that the fans brought from the FST future) without him knowing, giving him a more menacing appearance, so that the doctor (who was controlled by Jacob) didn't try to cure Isabella, and he went to the Island.
But what not even Jacob knows is that the Eyeliner is a manifestation of MIB, like the Black Smoke and Jack's beard in the future (past).