my instructor and I ran a seminar for female self defence a few years ago where he demonstrated the effectiveness, or should i say ineffectiveness of a solid kick to the groin, he had the female kick direct and as hard as she could into his groin, (no stopping or thigh checking from him either) he then proceeded to take her to the ground, mount her and punch the floor padding beside her head a good 10 times before keeling over from the pain.
obviously the kick did work (he said he went purple the next day and couldnt walk properly for a good few days) but there was a delay before he could not function any longer.
for females attacks need to be precise and downing in one, a shot in the groin is going to be effective, but more likely than not the lad will be angered and knock you out before being downed. then once he comes round from the pain he is going to do whatever he wants to and hes going to be super angry..