Lee manages a series of short, quick kisses because she's laughing and it's stretching her mouth out and that makes it hard to make a proper kissing face. She has to pull away because this is a disaster. Least romantic kissing ever, good job everyone. You never see anyone in the movies have to stop because they're having a fit of the giggles.
"We messed it up." She's still holding his hand, reluctant to let go.