How hard is Vayne?

Somewhat.

I remember when I tried Vayne a long time ago, and I was 100% obsessed with trying to pin people to walls, so I kept going in and dying

But if you're not like me, she's pretty simple to use; dash in for a poke or away to escape, pin people whenever you feel like it

You can either go full crit because your ult gives you a shit-ton more AD, or full tank/speed because your passive will do a shit-ton of damage if you can stay alive

if you can't auto cancel don't bother

She's not awfully hard to play decently but don't expect to master her in any short time frame as lining up condemns is, imo, one of the hardest things that exist in this game. Other than that the mechanics are the same as any other adc and if you can play Lucian then it's not that much harder.

She's not hard at all. I was lagging my very first time playing her, and went i think 0/8 in lane? Long story short I finished two items and got 14 kills before I died again.