Gwen Stefani has created a line of dolls dressed in outfits like the ones her and her Harajuku Girls wore on her last tour.

This sentence contains a pronoun case error. The prepositional phrase "like the ones her and her Harajuku Girls wore" contains a compound subject ("her and her Harajuku Girls") and a verb ("wore"). To test the case of the pronouns, separate the two parts of the compound subject and pair each with the verb:

• her wore [This does not make sense.]
• her Harajuku Girls wore [This makes sense.]

The pronoun "her" can be in either of two cases: objective or possessive. In the clause "her wore," the pronoun "her" functions as a subject; this is incorrect. The feminine subjective personal pronoun is "she." In the clause "her Harajuku Girls wore," the pronoun "her" is possessive: the antecedent of the pronoun "her" is "Gwen Stefani" so "her" means "belonging to Gwen Stefani."

This version of the sentence corrects the error:

Gwen Stefani has created a line of dolls dressed in outfits like the ones she and her Harajuku Girls wore on her last tour.