There is a difference between Live version and PBE version which is in Elise's ability description. (I am playing on Russian client, not sure if it is the same for other languages) On PBE in addition to what is already written in her ability there is also a part which says "_Spiders apply Elise's on-hits_", while in fact, it doesn't seem to work.
* Get Elise (any level)
* Build her some items which have procs
* Let her build up mana and transform
* Watch as spiders attack their targets (of course they have to attack the one diff from Elise's target to see it clearly)
I personally tried Morello, Red Buff and Statik - none of them seem to work.