YOU SAID:

I like a boy who has a girlfriend

INTO JAPANESE

彼女がいる男の子が好き

BACK INTO ENGLISH

I like the boy with her

INTO JAPANESE

私は彼女と少年が好きです

BACK INTO ENGLISH

I like her and boy

INTO JAPANESE

私は彼女と男の子が好きです

BACK INTO ENGLISH

I like her and boy