Louise Merrick is the oldest of the three nieces of John Merrick.
At the age of seventeen, Louise has been shaped by her mother into a would-be society girl. She has been schooled to be attractive, graceful, a social ornament; this process has left her somewhat jaded and bored with her life.
Louise's late father was a younger brother of John Merrick and Jane Merrick. Louise's father Will was not a financial success; at the time of his death he left his widow and child only a life insurance policy. His family survives on the interest income from the policy, living a meager and scrimping style of life, until Louise turns seventeen; then, her mother launches a rather desperate project to win Louise a rich husband. Mrs. Merrick calculates that by spending instead of preserving her capital, she can afford a high-society life for herself and Louise for three years — enough time for Louise to land a suitable prospect.
This questionable plan is negated when Louise is summoned to the estate of her aunt Jane Merrick, as a candidate to be Aunt Jane's heir (along with her cousins Patsy Doyle and Beth De Graf). This begins a chain of events that revolutionizes Louise's life and resolves her financial difficulties. (Aunt Jane's Nieces)
After becoming a ward of her Uncle John, Louise is exposed to many positive influences; her character develops as a result, to the point where she rejects her mother's values to marry for love. Her social set being what it is, her bridegroom turns out to be wealthy as well. (Aunt Jane's Nieces in Society)
The fictional Louise Merrick shares one notable quality with Baum's sister Mary Louise Baum Brewster: she is a poet whose poems are regularly rejected by the periodicals to which she submits them.
When Louise herself becomes literary editor of the Millville Daily Tribune, she finds her situation reversed: she uses phrases from the rejections she has received from others to reject amateurish submissions to the newspaper. (Aunt Jane's Nieces on Vacation)