What is the appositive in mother Louisa making spaghetti?

There is no appositive in the phrase "mother Louisa making spaghetti."

An appositive is a noun or noun phrase that renames or identifies another noun or noun phrase. In this case, "mother Louisa" is the subject of the sentence, and "making spaghetti" is a participial phrase modifying the subject.

There is no other noun or noun phrase being renamed or identified.