the secret to beat vayne is just like twitch. don't fight. unless vayne ults or engages or you have vision on her. she is like twitch. great. great at cleaning up fights. but she sucks at dpsing down your team quickly like other carries. the element of surprise is whats going for twitch and vayne. they can't just. start a fight. they get one shot. they take advantage of you starting a fight and focusing other team mates. to kill you from behind or something
don't fight her team. fight her. if you don't see her dont engage.
also. don't split push against her . group. shes an assassin. don't stay alone in a long lane against her. her passive and ult move speed will catch up with your ass unless your a hecarim with ghost up