@Coookie:
Well, then explain to me how Marigold was able to form fire snakes.
How is Usopp able to form firebird stars? It's shonen fiction, where moves are stylized beyond what would happen in life naturally. While there might be an explanation for what she did, I would say that she was using Haki to avoid damage from the fire* and using her natural abilities and strengths to push that fire as an attack with a typical shonen stylized form. No, I don't think this qualifies as a "shonen excuse" simply because there are a ton of things like this in the comic that aren't designed to have an explanation outside "it looks cool" and it makes the attacks more interesting. Perhaps its a combination of her Haki allowing her a greater defense, her having a cobra DF that can spit crazy acid and probably do other crazy things, being really strong, and stylized action.
*@Tenryuken: She didn't "create" the fire magically, she had a match in her hand. Also, you have to understand last chapter we were essentially shown that different people have different strengths and skills when it comes to Haki. Granted we weren't shown in depth, but Sandersonia clearly was somewhat unique with her "Mantra"-like ability, while Marigold clearly was somewhat unique with her "Tekkai"-like ability. While we know both were Haki, one exhibited an ability the other did not. IE: Sandersonia never claimed to have a heightened defense, and Marigold never claimed to be able to read Luffy's movements. Hmmm, "Tekkai"-like ability. Hmmmmmm. More thoughts on rokushiki being closely linked to Haki.