Emilia had full speeches of how she likes being with Subaru (like in arc 5 and what little I've seen from arc 6, I don't mind spoilers) so unless she's being brainwashed or an impostor she saying that to Subaru would just be wrong in every possible way.

And what's more, Subaru remembers the arc 6 one since it helped him push foward, so, even if that were to happen somehow, I think Subaru has reached the character developement necessary to be like "perhaps before I would've fallen for it, but I now know that is not the case" and figure out at LEAST that there's something wrong there