She's scary. Very very scary. I'm always at her ult range if i wanna attack and they usually save their ult for me most games.
Banshee's veil would help but when she gapcloses and triforce bursts me, its way difficult.
Be aware of her incoming ganks through warding during the laning phase. If she's going to Ult you anyway, force her to go under your turret at the least.
You have no CC. That means your support needs to do their job and protect you; preferably by stunning/knocking-back Vi after she finishes her Ult, when she's stuck under your tower.
Every other person on your team is there to help. If your support can't stop her, a top with Teleport a roaming Mid or an on-time Jungler is there too. This is how you win a bad matchup; by utilizing your teammates.
don't bother buying early armor on a adc, if your having so much trouble you or your support should buy sightstones and ward your side of river, thus being safe from any threats of vi coming in. also her ult range isn't that huge, but she can easily get close enough to use it.
In team fights you shouldn't be close enough for her to ult you, and if she does then SHE should be out of position and bursted down shortly after.
Work in your positioning and make sure you aren't dragging her threw your team if she is going out of her way to ult you every fight
