Suggested by Sonic Sinestro’s greatest advantage here is that the GL Power Ring can create actual fire. Whether it can do this directly or if it has to be by first creating a flamethrower is debatable but it is helpful in this fight. Ultimately the reason why I would still give Miss Martian the edge is thanks to her great strength. She was able to land solid hits on Supergirl back in the day which is enough power to break through Sinestro’s constructs. Miss Martian wins.