Lee tells herself to calm down, to slow the rapid hummingbird beating of her heart. Nothing has to happen if she doesn't want it to. And she knows what to do now more or less, even if, okay, theory is not the same thing as practise, at least she's not going into this blindly. And if she doesn't like it or doesn't feel like she's ready, she can say no and he'll stop.
Repeating all of this to herself doesn't make her less nervous. Why isn't it working? Stupid brain.
Her hand moves down, hovering around the hem of his shirt like she's deciding if she wants to go there. The pads of her fingers press in the gap between fabric and fabric, feeling the skin there, and that seems to settle it for her. She presses her palm flat against his stomach just underneath his shirt. This is usually the part where they get interrupted, and she's tense for a few minutes - but when it doesn't happen, she starts to relax again.