And it’d be reeeeal weird to have a ~17 year old Ben Solo address Rey as ‘sweetheart.’
It may not be from the past, it could very likely be said by him in the future, possibly in The Rise of Skywalker. Afterall, her vision did foreshadow their duel on Starkiller Base.
Maybe we should wait and see what happens in TRoS. If Ben says something like that, or if we learn something new about Rey’s parents then you could extract a line from there and put it in TFA or record a new line based on what we know.