The phrase is deliberately chosen. Sex with Sherlock could never be just about the sex, just about his body and hers. She's not just offering him her body, she's offering him all of her, her body and her soul.

She kisses him back, and steadies herself against him with her good hand on his shoulder as he lays her down. Once she's settled, she reaches for his belt as she kisses him, undoing the buckle.