This is a YA book from, I believe, the 80s. It’s about a preteen (named Sunday or Sundae) whose mother gets her an agent, so she can audition for TV commercials. I remember that her signature look is a French braid or two braids? She has some difficult auditions including one for peanut butter where she has to do a cartwheel,  and the directors loudly discuss how awkward she is in front of all the other girls. She eventually makes a friend who is a young actress who is obsessed with Virginia Woolf’s suicide,  and eventually she finds the friend by the ocean wearing a raincoat stuffed with rocks contemplating suicide. I think the book was called Incredible Sunday, but I haven’t been able to find it under that name.

Thanks so much!