Dunno about being the first but I think she did declare of going toe to toe with Nanako right to her face in Vol 10thanks for the chapter!!
btw, is this the first arc where Su Luxia is outright stating that she's going after the villain/villainess? Honestly I like it, it's refreshing.
she didn't outright say that at first though, Nanako and her was doing the whole passive aggressive thing for a while before fighting against each other fr.Dunno about being the first but I think she did declare of going toe to toe with Nanako right to her face in Vol 10