I will first tell her that school is our second home.
i think she will agree
then i will tell her that class is our own room and in ur home and ur room u dont shout or talk loudly then why in class.
then i will also explain her that she is not only the class evry 1 are present there and everyone gets disturbed with her so pls converse politily
the person she is talking to is in front of her.
i think it is surely enough to explain her