Marcel Proust offers, in vivid detail, a narrative of his childhood in the first section of Swann's Way, titled "Combray". Throughout his story, he offers poignant facts about secondary characters in his life, such as his aunt Léonie, in a way that demonstrates that, even those peripheral personalities, are equally important in the formation of the strange, unique and complex man that Proust becomes.
Aunt Léonie is, indeed, a comical character. Proust does not directly mock her with any purpose to humiliate her, but he does point out her extremely quirky nature: her obsession with death, the wild youth that her family would never acknowledge, her hypochondria, and her penchant for dipping a madeleine cookie in her tea.
And suddenly the memory returns. The taste was that of the little crumb of madeleine which on Sunday mornings at Combray [..]
This latter habit was one (of several) which Proust would grow up doing for Aunt Léonie, and which he would later on adopt it as a habit of his own. He would call this "the whole world in a cup".
While "Combray" is the only time in the novel where Aunt Léonie will appear, her characteristics are strong enough to be learned by Proust for life.
My aunt had by degrees erased every other visitor’s name from her list, because they all committed the fatal error, in her eyes, of falling into one or other of the two categories of people she most detested.
As the reader will later realize, Proust's own quirky behaviors are nothing but a repetition of those of his aunt's.
The reader may be able to relate to the relationship between Leonie and Proust at many different levels. We all have had, at some point, a family member who is considered "odd", "off" or "different" by members of the same family. Like Prousts's criticism of his aunt, his aim is not to show rejection, but to acknowledge her strange uniqueness while, subtlety, admitting that many of her flaws are also shared by him.
In all, Proust gives us a candid, almost loving, description of someone in his family which is meant to be described as a very difficult individual. Instead of pointing at her quirky ways in a negative way, he just tells us about it the same way that one would tell funny stories about some interesting family members. Nevertheless, from snooping out of windows, to feigning illnesses, to making "people lists", to having her specific way of having tea, there is no dull moment with Aunt Léonie. It is no surprise that Proust sort of perpetuated her rare traits in his own personality.