From Chapter 12 of Persuasion: “Without emulating the feelings of an Emma towards her Henry, she [Anne] would have attended on Louisa with a zeal above the common claims of regard, for his sake; and she hoped he would not long be so unjust as to suppose she would shrink unnecessarily from the office of a friend.”

The reference is to Matthew Prior’s Henry and Emma, in which Emma expresses abject willingness to serve the non-existent rival with whom her Henry pretends to be in love in order to test her.