OK. Here is the way I would deal with it.
Rotate the image 90 degrees using the Motion Effect. That is your best way to rotate it as far as I can tell.
Scale the image down on track two to see the entire thing which will give you black bars on each side. Fill the background with a pretty motion background using the colors of the wedding by putting it on track one. You may find the shooter left lots of room around the subject on the sides, so you may not have to scale it down all the way.
In the area of the video with the motion background, superimpose small closeups that were taken by the photographer during the wedding. You can restrict the images to the area over the background, or you can float them slightly over the edge of the video so they look like they are actually floating. Use a drop shadow.
There is no magical way to make a portrait shot into a landscape shot. No magic at all. Zooming in can’t be done without loss of quality. So make it look like it was done on purpose. Use baby pictures if you need to. Pictures of the ceremony. Frozen frames from the movie itself. Use your imagination.
Just don’t expect it to look like it was shot normally.
Steven
https://www.stevengotz.com