In a roller-blading mishap, wendy fell down and injured the very back of her head. which of her senses is most likely impaired?

The senses most likely impaired is her vision. 
Vision and eye problems are quite common following a head injury. Symptoms that could occur are blurred vision, difficulty focusing or sensitivity in the light. Wendy in particular injured the very back of her head and this is where occipital lobe is located. This is the brain area which contains most of the visual cortex and is responsible for vision processing.