Having worried at the “Meereeneese knot” and not making much headway, George R. R. Martin reports that he turned his attention to completing a chapter for another character who is “far away from Meereen” and whose second chapter wraps up her part of the story. GRRM finishes claiming that he has 38 POV characters to go, but that’s certainly a teasing joke on his part. Speculation as to who the character whose final chapter was completed is can be found below.
Given what GRRM has previously revealed, it seems possible that the character is Asha Greyjoy (whose chapters were going to extend into A Dance with Dragons) or possibly even Melisandre, whom GRRM more or less revealed as a new point of view character for that novel.