There wasn't much for her to grab. Being stabbed to death with a needle would probably be humiliating and annoying on top of painful and slow, and that would be about the most effective weapon beyond the vial, sterilizing swabs and box of bandages. Maybe being beaten to death with a box of bandages would be kind of ironic on top of humiliating, annoying, painful and slow. Creative options, really.
Still, he didn't stop her. He had presented his compromise, and knew fighting her on it wasn't the effective route, even if he ended up with a needle in his neck. Instead, he tensed against the attack, both hands raised in surrender, compulsively leaning away though he kept his gaze level on her. If she didn't want to play this game, she didn't want to play this game. Fine. He could have S.H.I.E.L.D. agents trawling these cliffs in minutes.