The metal part is the trim piece because there isn’t a coordinating trim piece for this tile. So, the corner round exceeds the trim piece. Hope this makes sense.

so the drywall sits proud of the tile/trim piece? nobody saw that was going to be an issue while they were tiling???

can you just remove the trim piece and wrap the tile around the corner and do that small wall?

or, cut out the wall in that area and set it back further so it's flush w/the trim. Unless you can find a larger trim piece that will let you run the dry wall under it on the wall side.

No hammering! Really? This wall wasn't properly considered from the beginning probably. I think Beth had the best idea, wrap the tile around the corner and wall to the back wall. That isn't the proper Schulter trim edge either so I fear you have a tile person who doesn't have the skill set to do your job.

Make a new sill out of white solid surface with a returned end for white solid surface "L" molding, covering the wall and metal molding, to die into.

Smart man, Joseph!

The metal profile edge should have been install even with the face of the drywall. Plaster over the radius to the profile edge. Just have the vertical end wall redone. Poor planning and take away his hammer.