Is using Weird Woods to give damage to someone considered an "attack" on that person? One of the Shadows's special ability is to be able to attack back when attacked. So I was wondering if I used Weird Woods to give 2 damage to that Shadow, would the Shadow be allowed to attack me back?
No. See this thread Counter-Attack and Blood Sucking. An attack for the purpose of triggering a counterattack is only when you choose to attack a player on your turn and roll dice.