When they fuck (and it is fucking, because neither of them is quite ready for it to be anything else yet) Buffy still sees it. Not so much when Faith is looming above her, thrusting so hard it almost hurts, unrelenting, smirking as Buffy whimpers and moves frantically against her, wanting more, wanting it to never stop, wanting Faith. No, when that's happening Buffy doesn't see fear, she only sees lust and wanting and arrogance, sometimes a small flicker of residual hate or something else, something unidentifiable, something almost warm. Whatever it is, she's beginning to like it. But that's not what she looks for.
She only sees it when she rolls Faith under her, when she skims her hands over skin, feeling muscles clench and flutter under fingertips, when she watches Faith arch into her. When she kisses, softly, every bit of skin she can reach until Faith is squirming and looking at her, confused. Then Buffy asks permission. Every time, she asks. She doesn't think anyone has ever forced Faith, but she doesn't think anyone's ever asked either.
Faith always says yes, and Buffy moves in her, still slightly clumsy and unsure, but she moves, works Faith's body, makes Faith strain against her hand. She pushes her whole body against Faith's, feels skin and sweat, and as Faith comes close she grips Buffy's shoulders, wraps her legs around her waist and they move together until Faith comes, eyes closed and gasping.
It's after that, when Faith opens her eyes, that Buffy can see it. Only for a moment, but its there, small cracks form in her mask, and Buffy can see the desperate fear, the overwhelming terror. She wants to comfort her, but Buffy still doesn't know what Faith is afraid of, and she's too scared to ask.