>>11395444
>I assumed it was water inflation, the best way to "Put out" a fire girl is to pump gallons of water into her until she's too waterlogged to make any fire
That's one angle to approach it, but I also like the idea of a fire-type to have such a high internal temperature either as normal or when worked up that foreign fluids boil off and aerosolize inside of them until they swell up into a steam balloon, so on the milder side of that interpretation you could have her boozing it up until she's blotto and bloated. You also get the great synergy of steam eventually jetting out of her and whistling at the higher end of things - or take it to its natural conclusion of pumping her nonstop, steam jetting from every orifice with a shrill, rising whistle as she stretches and swells until she finally bursts into a cloud of steam vapor as the whistling reaches its screaming crescendo.

Also a fun if short-term combination? Fire girls afflicted with blueberryism, Someone posted a comic of a berry MGE baphomet cursing another girl with it a while ago and I soon started wondering about if someone like a Hellhound got hit with that.