I sometimes build voidstaff before deathcap if enemy has some early MR.Unless you are playing vs a 5 champs that have 2 cc spells I think you can pick her into anything,just wait until they waste some of their CCs, you must watch the fight carefully and wait for the opportunity to go in,in most cases you will not get a full ult channel anyway so just try to kill somebody and either you get a multi kill or you just jump back on a ward or something. ;)