Even a martial arts expert is going to get cut if facing an experienced knife fighter.
You should NEVER expose the palms, as a cut tendon is incapacitating.
Use backs of hands in defense until able to get sufficiently inside to put them down with (unarmed) fighting.
Speaking of unarmed; there is a saying in the Kungfu world: “He who goes to fight a T’ai chi swordmaster unarmed, will return unarmed.”
We are talking about an effective response to a woman being grabbed. The proper response to an experienced or inexperienced knife wielding assailant is to shoot the bastard. Unarmed combat vs an armed assailant is stupid especially when older. Shoot first, shoot fast, shoot accurate.