The ending of A Quiet Place: Day One has Sam giving up her own chance of escape so that Eric and Frodo can reach the boat. She sets off car alarms to pull the creatures away, and Eric makes it onto the boat, where Henri is also aboard. The film then leaves Sam alone in the city, playing Nina Simone's Feeling Good out loud as a creature closes in behind her. Her death is implied rather than shown.
What was the point of the film, then? In my opinion, it is a story about how a dying person chooses to spend her last hours, with the invasion as the pressure that forces the choice. Sam's requests, the jazz club where her late father played and a slice of Patsy's pizza, are small and human, and the film never gives her a heroic mission.
The comparison with the earlier films is where the ending earns its place. A Quiet Place (2018) opens with Beau killed after he switches on a noisy toy, so sound is the family's great fear from the first act. Sam does the opposite on purpose. The car alarms are, in my view, the cleverest set piece in the saga, because they turn the creatures' one weakness into a tool of mercy for someone else. Perhaps that is why her ending lands as a choice rather than a defeat.
The connection to the later films is the sea evacuation and Henri, who also appears in A Quiet Place Part II, where Djimon Hounsou is credited as Man on Island. That small thread tells you survivors do get away from Manhattan, even if Sam does not.
Does the cat die? No, Frodo survives, and Eric finds Sam's note asking him to look after the animal. Perhaps that is the gentlest beat in a franchise that rarely offers one.