The Grimes gang are years in the future though.We didn't actually see her die, IIRC, and she did know the way out. Maybe one of the remaining cars had the key under the visor, or she knows how to hotwire? Not assuming this is the case, but this franchise is not above reuniting characters in highly improbably situations...
As that article above points out, at this point the show is TWD West: Los Angeles is as Atlanta was. The boat could be interesting wrinkle. Coming ashore only to scavenge would be a good survival strategy, and undoubtedly there others doing it. But it's hard to imagine the plot taking that route long-term--and it would likely be frustrating because production would force them to stick to the same and similar locations rather than, say, sailing to Hawaii, or another continent.
However, the opportunity the show has is not being bound by pre-existing material in the same way TWD is, however loosely. If they wanted to, they could jump back in time again--most likely via characters Madison, Travis & Co. would meet later. Maybe someone in the media who had detailed knowledge of the early and progressing reports; maybe a conspiracy theorist who was actually on to something; etc.
Or they could all hitch a ride on a train with a cow-catcher and head cross country to meet up with the Grimes Gang...
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