Whenever Evie describes her mother, she brings up her glamorous red lipstick and how much she wants to look that amazing in it:
"I want to wear lipstick," I said.
She took a cigarette pack out of her apron pocket, then her gold lighter. She tapped out the cigarette, then placed it between her lips and lit it up. She took a fleck of tobacco off her bottom lip. She was wearing Revlon's Fatal Apple lipstick—the most tempting color since Eve winked at Adam. (3.8-9)
For Evie, her mother's red lipstick is an indication of her womanhood and her sexual appeal. Unlike Evie, who is gawky and still seen as a little girl, her mother is attractive, confident, and effortlessly glamorous. To Evie, her mother's dark, lustrous red lipstick symbolizes exactly what a woman should be—and it represents the kind of woman that she wants to be someday.
However, the red lipstick also comes to represent her mother's lies and deceit when it comes to her family. When the police find the house that Peter Coleridge broke into, they also find a wine glass with red lipstick on it—Bev's red lipstick, to be exact. Evie comes to realize that her mother has lied to them all and was seeing Peter behind their backs. Check it out:
There were glasses left on a sill. Two of them. One of them had lipstick traces. Dark red, the paper said.
The most tempting color since Eve winked at Adam. (28.13-14)
In the end, Evie uses the same red lipstick to lie in front of the courthouse that she was the one who was meeting up with Peter Coleridge—and perhaps as a way of letting her mom know she's onto her. The red lipstick no longer bears the same appeal to her, and by the conclusion, Evie even decides that she no longer wants to be anything like her mother. And in this way, the lipstick works as a symbol for Evie's relationship with her mother—as her regard for her mom decreases, so too does her fondness for her womanly icon.