How do I play in this situation?

So recently I picked up Fiora, first 20 games were kinda rough for me, but now I think I got her down mechanically. The problem is, quite often I get into these situations where Im playing vs a tank , something like Maokai etc, I roll them in lane getting a cs lead and a kill or two, but my team gets completely destroyed elsewhere.

Then Im faced with a situation : If I try to help them and go teamfight, I will obviously get cced to death, and blown up by a much more fed team. If I try to splitpush, they will either send their support + adc to stop me, which I can't beat 2 vs 1, or they will send their tank to hold vs me, even if the tank is behind an item, and maybe a level or two, he usually still can atleast hold vs me, and if atleast 1 more dude showns up Im guaranteed dead. Meanwhile my team is so behind that they won't be able to win 4 vs 4 or even 4 vs 3.

So what are my options in situations like this? Do I try to build more tanky, which is pretty uncommon on Fiora and try to teamfight? Or just not play Fiora into tanks? I just don't know what Im supposed to do anymore lol.