Who are Susan Heffley's sisters? How many are there? What do they do for a living? Do they have kids? Help me!!!

You haven't cited a novel title for this question. I am unable to help you without one.

Susan's sisters are Aunt Gretchen, Aunt Cakey, Aunt Audra, and Aunt Veronica. From the text,

"Mom's oldest sister is Aunt Cakey, who isn't married and doesn't have kids. And that's probably a good thing because its pretty obvious she doesn't like kids."

Aunt Gretchen's story:

"Mom's youngest sister is Aunt Gretchen, and she's the complete OPPOSITE of Aunt Cakey. Aunt Gretchen has twin boys named Malvin and Malcolm, who are TOTALLY wild. In fact, they're so out of control, Aunt Gretchen used to keep them on child leashes."

Aunt Veronica likes to appear on video conferences.

Aunt Audra is another weird story:

She likes to believe in crystal balls

Thank you Julian.

Aunt Gretchen

Aunt Cakey

Aunt Audra

Aunt Veronica