Yes, if she wants the confirmation, she should resign from that club membership.
I really don't have a problem with gender-exclusive clubs as long as they are not purposefully barring entrance by the opposite gender nor trying to obtain monies, powers, or resources for one gender only. If they are gaining membership simply by not inviting the opposite gender, there is no harm in that.
But when someone of the opposite gender asks for membership and they are denied based on gender, then that is where I have a problem. Or if one gender only is receiving benefits of the club's existence.
I am a former member of Alpha Delta Kappa - an international professional women's organization for educators. We mentor new teachers, give scholarship monies to student teachers, tend to the academic needs of impoverished children and lower income schools.
We are female only. I had no problem with that until we had a young man who was a student teacher who received scholarship monies from us. A few years after he graduated, we discussed breaking the international mold and offering him membership. He, knowing nothing about all of this, was denied access.
I resigned ..... sadly.