Completely forgot about that part from chapter 1. The choice should be pretty clear, assuming that the "disappears" part means she simply goes back to her home universe. Still wouldn't feel right if MC falls for her unless it's revealed that he was meant to die and never end up with the Sui in his world anyway.Nope.
“Multiverse no Watashi, Koishite Ii desu ka?”, chapter 1, page 58—59: