What is a "Woman" The topic goes into discussion about toilets and the trans issues. As a couple of people have pointed out already, gender neutral toilets are a possibility. Such facilities already exist in places like coffee shops, and make no binary distinctions based on genitals, appearance or chromosomes.
The question of what is a woman goes back to comments by JK Rowling and culture wars. After many successful attempts to bring acceptance of trans issues and people who don't fit into the binary, there is a current backlash. It seems to often revolve around the right of cisgender to suggest that people, mainly women, are likely to be offended, especially by people who began as male, biologically, in women's spaces.
This idea is not new because it was raised historically by lesbian feminists but it is now perpetuated by the media. It rests on an assumption that men can rape women and that a pre-op male to female could rape a female potentially. It is sometimes backed up by concerns about transwomen who have committed sexual offences, which portrays a negative stereotype of a transwoman rather like the film, 'Silence of the Lambs.'
With the current focus on 'what is a woman' in the media there is a question how far it will go in ushering in a backlash. I read recently than in South Korea there is an introduction of legislation to allow police to inspect the genitalia of transgender people in toilets by a member of the police of the person's assigned gender. There is also a lot of hostility to LGBTIQ throughout the world, so any genuine philosophy discussion needs.
The attempt to ask what is a woman, which is sexist without the equivalent one of what is a man, can become shallow if it is simply about trying to reinforce the binary. It is this strict binary division which may drive people to 'fit in' as opposed to a more critical and fluid understanding of gender stereotypes about behaviour and bodies.