In this case, Rosa is the name of her neighbor, instead of the person I'm talking to, right?
You can change the suffix "ha" with another name. Here you are talking about a person related to another person
This course has been pretty consistent about using ي when we are addressing someone by their name: if I were talking with my friend Rosa about our friend Samia, and Samia's neighbor walked up to us, I might say هٰذه
جارتها، ي روزا
vs if I were talking with my friend George about our friend Rania (who lives next door to a Rosa), and Rosa walked up to us, I might say the given sentence.
(At least, I think that's how it works...)