Looks very similar to mine. Try using the word "bars" instead of fence and the prompt sort of works. I think Ai understnds what being behind bars means-but maybe not what being behind a fence means. Here is a link where I tried "bars".
"white grid fence with 1 inch wide slats over a watercolor painting of a smiling brunette beautiful woman. the fence follows the contours of the face."
Looks very similar to mine. Try using the word "bars" instead of fence and the prompt sort of works. I think Ai understnds what being behind bars means-but maybe not what being behind a fence means. Here is a link where I tried "bars".