I think it's difficult to say that she's going downhill on the basis of the only track released since Paradise, and a seemingly phoned-in video. If you disliked Paradise, too, then fair enough, but I think that judgement should be reserved until we have more substantial new material to make an informed statement. Both Young & Beautiful and this video have quite clearly not been her primary focus; considering that this track is lyrically adapted for the movie rather than a bespoke creation, and that the video was likely done inbetween recording sessions, photoshoots, possibly touring (if having to "re-record" is accurate) then she's obviously going to stick to what she knows, play it safe, and not devote all of her time and attention to it.
I do agree that Young & Beautiful and this video are far from her best work, but I wouldn't use it against her just yet.