When playing an event with cost X, the value of X is set before applying modifiers to the cost, so Littlefinger’s Meddling will reduce the cost of that event by 2 without altering the value of X.
Some events have additional abilities that can only be triggered while the event is not in its owner's hand (for instance, The Prince's Plan). Triggering such an ability is not considered to be "playing an event," therefore the cost of such an ability will not be reduced by Littlefinger’s Meddling.
Does this plot also reduce the cost of shadow events? Or is it "bring out of shadows"? — kuwalek 27
It does. Playing events from shadows counts as "playing" and as "bringing out of shadows". — Odrl 1164