head rest doesn't fit small person

The Prius hatchback headrests have been filling this need. I can't promise that the 2015 models are still the same, but stop by the dealer and swap them around to see.
Here's one at a fraction of the cost the dealer will charge:
2014 Toyota Prius Head Rest Dark Gray Fabric Front Left Right 13 14 | eBay

 

try turning them around

 

try putting them all the way up. it's way more comfortable for short people....

 

Head rests - 2013 Prius v owner. Be careful about turning head rests around. They slope so much to the rear that one needs to be concerned about the effectiveness in the event of the rear-end collision - the head movement backwards being too great and resulting in the whiplash we are trying to avoid. Not sure what the problem is. I am 5'6'' tall & wife is 5'1'' tall - short enough that we use Costco car seat cushions for added height. Head rests are not a problem, although, we do 'rake' the seat backward a little bit - enough so are arms are slightly flexed at the elbow. Some people really crowd the steering wheel (not safe do to air bag function) and that would cause the head rest problem.

Head rests - 2013 Prius v owner. Be careful about turning head rests around. They slope so much to the rear that one needs to be concerned about the effectiveness in the event of the rear-end collision - the head movement backwards being too great and resulting in the whiplash we are trying to avoid. Not sure what the problem is. I am 5'6'' tall & wife is 5'1'' tall - short enough that we use Costco car seat cushions for added height. Head rests are not a problem, although, we do 'rake' the seat backward a little bit - enough so are arms are slightly flexed at the elbow. Some people really crowd the steering wheel (not safe do to air bag function) and that would cause the head rest problem.