vayne is a hypercarry, like tryn.

beast lategame

She gets countered but is not UP. In lane she is not great, but even when she is beaten in lane, she can easily farm and then become powerful late game. So at times she is OP but in general she is balanced.

She is a champ that requires skill because your early game is bad but you can almost win against any AD Carry if you play right.
Midgame same.
Lategame you must be careful to not get stunned due to your pretty Low range but if you are able to deal your damage, it's over same for every other AD Carry...

I would say if you like her kit, you should play her and you will succes easily if you know what you are doing.

She need some health deadly !!

She got Poppy-zoned.