hahaha, though I agree that Carmen will most likely become the Mc's childe, it will not really make a difference if MC and C are just a slight interference at best in that fight. Now in the very unlikely event there is something incredibly special about Sharon's yellow eyes and they can be used on vamps as well there might be a twist there, where either Sharon or Laurie or maybe both of them together can buy a second that could swing the outcome.
I see Carmen getting turned more for harem purposes and how human or inhuman maybe MC turns out at end as really being instrumental in Ragnarok. Maybe she could help against Virgil if you are right or another that might be Arcas if he makes an entrance in the game. Her having another secret that could make a difference like being also part werewolf is kinda unlikely with no hints or progress in that direction in game.
Then it is even more likely that who Sharon's sire was and his/her line will ever play a role, which by now seems pretty unlikely beyond maybe some subplot about dealing with the Archons and princeps at this moment.