@KiShiDo:
And if we know that the sister is matching herself without feeling pain and she is using Haki why not?
But you seem too simple-minded to realize that both sister have different types of Haki.
Yes there are different types of haki, I never said any different. But Oda typically makes it clear what they are doing, by having the characters show and talk about their power. "you can't hit me" - "I can read your moves", etc. Why can't it just be the scales of this particular snake that are fire resistant. It was even a named technique called "salamander", maybe she just practiced it.
Everything is being tied to haki, while it shouldn't - I mean it could be, but until it is confirmed somehow, I doubt it.
Rayleigh: pretty much confirmed haki, same as shanks.
Sentoumaru: he has haki like the denizens of Amazon Lilly and he could negate Luffy's DF ability - it wasn't really confirmed in the manga, but it was confirmed in the anime which I think Oda has some say in.
Fist of love: maybe he has haki, maybe a DF, maybe it was a gag?
Rokushiki: this was just martial arts, I don't see why this has to be haki. I mean Coby could do soru aswell, is he a haki user now aswell? I thought the amazons said almost noone outside of their island knew how to use haki.
mantra: this was tied in with the ability to "hear things", not necessarily haki, even though it has a similar effect. But I doubt Sandersonia (or was it Marigold) can hear everything that happens on Amazon Lilly aswell, so it's probably a different thing.