She's no burden to him. Two Amberites together can lift a large car if they choose to, so one human female is no bother. He just straightens, then drives his knife into the earth with force, then the other, arms length above his head. He uses them to lift them until his arms are straight, then braces his legs on the side, pulls the knives out and repeats the motion.

It only takes about five minutes for him to lift them both to the top this way. And strong though he is, he's breathing heavily by the time they get to the top. When they're there, he just stands until she drops off him, then hands her knife back, twists Shadows until his bow is back and starts walking up the tunnel again. All in silence.