My memory isn't that fresh about this, it's been a while since I read that chapter of the WN but IIRC, we don't see the exact moment Ram meets her but rather there's a point in the beginning of season 3, I think, where they visit Rem's room in the mansion and Subaru asks her "So now are you finally believing that she's your sister" (or something like that) and she answers with "Our likeness is uncanny but until I meet her for real I can't be certain" Later in the WN, Ram begins to grow a bit closer to the sleeping Rem and begins to desire to wake her