The scenario you described, where a girl slides down a plastic slide and her hair sticks up as she exits, is an example of friction.
When the girl slides down the plastic slide, there is friction between her body (which may be neutral) and the surface of the slide (which is also neutral). This friction can cause electrons to transfer from one material to another, resulting in the girl becoming negatively charged and her hair, being made of a similar material, experiencing a positive charge due to the attraction of the negative charges. This results in the hair standing up because like charges repel, and the strands of hair repel each other after being charged.
So, the correct answer is friction.