It was I who ~~bridged your minds~~ suggested changing that line to “we’ve become a dyad in the force”. I think it would help tie TLJ and TRoS without either undermining the other. The ‘dyad’ concept is left pretty ambiguous, but to me it seems to be analog to Kylo and Rey’s growing relationship (“The life force of your bond” as Palpatine puts it). Even if that’s not the ‘official explanation’, we could lean to that concept and make it so that the ‘dyad’ is something that forms between them, so to speak, sometime during or after TLJ. That way TLJ can keep it’s consistent story, and TRoS can do it’s own thing. And as Hal said it would help explain how Palpatine could be so surprised, if the ‘dyad’ is a new piece on the board.

As for the “what girl?” line in TFA, it never seemed to me like there was anything concretely important about it, it was just Kylo being a pouting teenager. Though it’s open-ended enough that it could be taken at face value or expanded further (much like all of TFA’s ‘mysteries’).