Turtle really puts her foot in it when she points out how Sydelle uses her crutches to get attention, but in a way she's only saying what everybody else has been thinking. Turtle means that Sydelle uses her fake limp and her coordinated crutches – symptoms of her imaginary disease – to make sure that people notice her. It's true, but it also hurts Sydelle's feelings. Angela covers for Turtle by saying, "She used the word crutch as a symbol. She meant, you know, that people are so afraid of revealing their true selves, they have to hide behind some sort of prop" (12.36). The thing is, Angela's really not making things any better; Sydelle's use of her crutches is both literal and symbolic. Instead of trying to stay hidden, she's using the crutches to make people find her.
Crutches don't always have to be literal, though. In Chapter 12, Sydelle accuses Turtle of using her "big mouth" (12.37) as a crutch, while Angela secretly thinks that Turtle relies too much on her braid. While Sydelle's right that Turtle does hide behind her big mouth, Angela's more correct: Turtle uses her braid to interact with people in ways that are very similar to how Sydelle uses her crutches in her interactions. Turtle almost taunts people with her braid. Sometimes it seems like her braid is begging to be pulled, but when people do pull it, she has the perfect excuse for kicking them. And we know that kicking people is something Turtle gets a perverse joy out of. Her braid also reinforces her identity as "Turtle," and it's only after she loses it that she's able to start referring to herself as "T.R."
Perhaps unfairly, Turtle's braid is taken from her before she's ready to lose it – it's burned off in the fourth bombing – while Sydelle just gets to stop using her crutches as attention-getters when she feels like it. To be fair, Sydelle probably wasn't planning on actually having to use her crutches, but she ends up needing to after she's hurt in the second bombing.