It's down to muscle memory, if you're used to dodging her skillshots you'll do it regardless of what they look like in a different skin.
I dunno, I have a really hard time telling her Q and her E apart which can sometimes make it hard to dodge one when expecting the other --- THIS IS WHAT I HATE A BOUT EVREY WEBSITE!! THERES SO MUCH PEOPLE READING AND POSTING STUIPED STUFF
Whenever a teammate plays against Lux mid she gets a Soulstealer with full stacks by 5 minutes.
Now that I think about it this is actually very true.
Lux is the only mid I own (mostly buy and play supports), so she's the mid I have the most playtime on. I've only ever had a soulstealer in a match once because usually I'm not winning lane hard enough to pull it off.
That being said, whenever an enemy Lux gets soulstealer it's always their first item (I get Athene's first) and my teammate always seems to feed them to the point where there's not much you can do to stop her.