Tocar vs. Tocarse

[aeclark2005]

Why is it "Ella se toca el pelo" instead of "Ella toca su pelo"?

[Rusty]

When one is touching one's own hair, the reflexive verb (tocarse) is required.

The other sentence says that 'she' is touching someone else's hair. The possessive adjective/determiner 'su' can mean 'his'/'her' (someone other than herself)/'its'/'your' (formal). So, the other sentence is quite ambiguous without any context.