I'm not sure exactly what you're asking but I'll try.
Yes I would be happy for a trans identified woman to come to a woman's event. Because she is a woman.
Am I happy for a man posing as a trans identified woman showing up? No, because he is a man.
So, it comes down to whether someone looks like they are actually a man, or if there is uncertainty. If I wanted a single sex space, I'd have to take that up with the group leader or the person themselves. Eg:
Steve, I notice you have a beard and refer to yourself as a man, can I just ask why you're here as this is the women's institute? Are you a trans man?
I guess if Steve said that yes, they were a trans man but have x/y/z reasons for attending the WI (or whatever single sex space), it's either
- Believe them - I'm fine, Steve doesn't post any particular risks to me and is after all, a woman, just of a different kind. His/her reasons for attendance might be legitimate (Steve, like me, isn't necessarily safe or comfortable in mixed groups and can't legally attend any men's only groups)
- Don't believe them - so Steve is actually a man, posing as a woman (posing as a man). WTF. Major red flags. Take this up with group leader. Avoid Steve. If very uncomfortable or don't feel safe, stop attending group and report the situation to WI.