Wicked Witch

She comes from the West.

She has mindless, flying monkeys do her bidding.

She casts sleeping spells, but snowfall from the Glinda the Good Witch from the North breaks the spell.

She uses fire to burn and scare.

She doesn't want the group to travel to Emerald City, and demands that the citizens there turn them over.

She hates water.  It melts and destroys her.

The protagonist kills the Wicked Witch from the West.

(This is on the DC Beltway).