To kill Sniper Wolf easily in the Snow Field area, use the stinger missiles. They not only reveal her location, but also home in and deliver a lot of damage. It will take about six stinger missiles to kill her, and you will probably never get hit.
-Although it is easier to kill Sniper Wolf with the stinger, it is fun to kill her with the Nikita remote controlled missiles.
-During your second encounter with Sniper Wolf, hide behind the ride that was on the far right as you came out the door . Fire a Nikita missile at her. You have to take the missile up a gentle slope or it will hit the ground and explode.