Regardless of how she had said it, she really, honestly, hadn't been implying anything sexual with that comment. She was speaking specifically of his muscles... the ones her head was currently resting on.
Of course, when he asked her to elaborate, she realized what she'd said and she couldn't stop a blush from creeping into her cheeks.
"Well, you know," she began explaining, "right here." She pressed her finger into one of his pecks. "Your muscles... the ones in your chest."
It was silly when you considered all they'd done in the past week, but she was slightly embarrassed and flustered.