I watched the video. It appears to me that he reached back to make sure she was behind him and she reassured him that she was.
Yeah, an "I got this" thing.
Anyone thinking anything nefarious about the interaction is totally forgetting the fact that BOTH Melania and Donald have spent their entire lives in front of non-stop paparazzi. They spent their lives in front of cameras. Neither would do something so uncouth as to swat the other's hand away while on the red carpet.
