Let It Burn
Fire can be cleansing, like when Adele sets fire to the rain. But it can also be dangerous, like when Jeannette Walls sets fire to herself. Or blows up a shack in the woods. Or probably burns down an apartment building in San Francisco. Or when Dad burns the Christmas tree or Uncle Stanley burns down Erma's house.
Um, yeah, there is a lot of fire in this book, and each time, it serves as one of those "what doesn't kill you makes you stronger" moments. As Mom says about Jeannette's scars, "She already fought the fire once and won" (2.2.4).
But there's more to it than that. You know how Mom is an "excitement addict" (3.14.32)? Early on, Jeannette too is "always on the lookout for bigger fires" (2.2.3). She's in danger of going down the same road as her mother, or becoming an arsonist hoodlum.
However, the excitement soon gives way to fear when Jeannette starts to wonder "if the fire had been out to get me" (2.7.12). Eventually, as she sees others setting destructive fires (literally and metaphorically), Jeannette seems to forget her firebug tendencies entirely. There is little mention of fire in the latter half of the book, indicating that Jeannette's dangerous attraction to fire has burned out.
That's one thing that separates Jeannette from her parents. They never really understand the consequences of their actions, but Jeannette does: she can see how destructive fire is, both to others and to herself. And that's one thing that keeps Jeannette's head above water and ultimately helps her get out of her crazy situation.