I thought this match-up was slightly in her favor tbh. I don't want to really add zoning as a factor since firestorms zoning is pretty fraudulent with the options being a high or a low that's pretty negative. He's pretty free to her oki air shenanigans since he has some weak anti air tools on wakeup. Lacking a 6f poke means he also has to deal with her pressure. d1xxMB breath
In the corner or close the corner this is in firestorms favor, of course. He has the highest damage output between the two so he doesnt have to open the other up nearly as much.