By the time Rita reaches Lambert, her assistance is no longer needed, so she merely hops off the bike and walks to join the rest of them in the middle.

"What the hell..." she breathes, struggling to believe what she just saw Childermass do. "That was your Spark you just-- are you okay!?"

A Spark is essentially a piece of a person's soul, and even if they take the form of flimsy paper things, they shouldn't be easily damaged or destroyed... but then, what Childermass just did, going against the Void and everything it instilled in him, it wasn't easy to begin with, was it? Rita's not sure what to make of the situation.