Responses
Although I may not be 100 percent sure this is right im 99 percent sure :)
-The watch made her go to an alternate world with same people but this world wont be attacked my the meteorites Everyone in her original world most likely dies from the meteorites (At least the characters that we saw, but tbh we will never know who survived and who didnt)
Hope that helped you even a little :)
I liked this manga very much, but I quite didn't understood the end, and so what happens to the others