Answer:
su
Step-by-step explanation:
A Rosa le gusta su pollo frito.
Translation:
Rosa likes her fried chicken.
In this case the pronoun related to the person "Rosa" is used, who is the third person singular of the feminine and therefore "su" is used
In Spanish, unlike English, there is no differentiation of personal pronouns according to gender for both "el" (he) and "ella" (she) is "su"