Many years ago, I watched my wife doing this with another woman! It was her secret fantasy to do it. So, it was arranged one night after a few drinks to get us in the mood!
She overwhelms her with her aggressive insistence, taking what she wants, knowing the older woman is ultimately powerless to resist her advances. How many times this play out in reality is anyone's guess, but MY guess very often, because women have innate lesbian desires no amount of conditioning can suppress when the right opportunity presents itself.