In French the possessive articles follow the gender of the noun, not the gender of the owner. For example we use “sa” with “voiture” (sa voiture) because “voiture” is feminine. However, “sa voiture” means both his car and her car, and mostly context will tell whose car you are referring to. But sometimes we need to be more specific:
J’aime sa voiture, je n’aime pas sa voiture – I like her/his car, I do not like her/his car
As you can see here, there is nothing that let’s the reader or listener know whose car you like and whose car you don’t. It’s ambiguous. To remove this ambiguity you can use a stress pronoun after the noun to nail down exactly whose car you do like and whose you don’t. Let’s try again:
J’aime sa voiture à elle, je n’aime pas sa voiture à lui – I like her car, I do not like his car
As you can see, by adding the stress pronouns (à elle = her, à lui = his) after the noun (voiture) we have removed any ambiguity. It’s definitely her car I like and his car I do not like.