Since you said 7C for Fiora and not low 7C, im guessing you meant you wanted to use the PROJECT Fiora key? Either way im going to use it since you said both characters are 7C.
Ok, so both Characters have things going for them. Weiss definetely has superior hax thanks to her summons, various abilities through her dust attacks and semblance, but Fiora has a few tricks of her own. Aside from being likely more experience with a sword compared to Weiss, Fiora's attacks can technically avoid durability thanks to Duelist's Dance (thought its hard to tell if Weiss's Aura would be affected that), she gains healing from said ability by targeting weakpoints, and by timing just right, she can become invulenerable thanks to Riposte.
It should also be stated that Fiora's armour can nullify magic, but IDK if this could be applied in this fight due to Aura being more soul related that being magic in RWBY, though it might work on Dust since despite being physical, Dust can't work outside of Remnant for some reason, so there's definetely something magical or esoteric about Dust.
Also, despite speed being equalized, Fiora can speed amp herself thanks to Duelist's Dance, Bladework, and Grand Challenge, and though Weiss can also do the same thanks to her time dilation, Fiora's is much more readily available.
I would say Weiss win's this more times than not, but given that Fiora's got a lot going for her as well, im going to wait until everyone else gives verdict before I give my final one.