if there isn't really anyone that's in a carry position in your team then it doesn't matter if it's ahri or ad galio
one thing you can do by yourself is to try trading ults with her, as long as you don't get killed in the process/bait your team to death. she's still scary with her ult down but nowhere near as much and you can use that time to catch up in farm and vision, maybe bully them out of a dragon or turret, whatever
also if corki doesn't want to group just play around that and defend and make sure you don't get picked while corki splitpushes or whatever. he's fed, you're not, so in the end it's in your best interest to help him.