Why not, though? Why is it okay (in your view) for the girls to discriminate based on gender but not genitals?
Because it fits her own needs.
Boudicca must not know that in every 30 person locker room of youth girls, there are very likely
at least 3 or 4 who experience sexual assault from a male, usually known to them. They often develop PTSD.
Their mental health and trauma doesn't matter to Boudicca because she doesn't even know it exists, how her presence may be a trigger, and actually believes that she is the one who needs to be affirmed by THEM...not knowing the severe damage it can cause.
Boudicca won't even concede for transgirls to use a separate single space area to alleviate the stress it causes on some of these females- again, because she doesn't know about it or, if she does, does not consider it as important as her own needs. She stated that these cases are female girls being discriminatory to transpersons instead of even considering other options like them coping and avoiding reliving a reminder of their trauma again and again and again.
No wonder many girls might just choose NOT to use those types of co-ed rooms, or may even change schools. I think most parents might do it quietly, or the girl will feign some drastic need to leave. Anything to get out of it with the least confrontation which could be just more triggering. That's why a lot of these cases don't get reported or brought to court. That process is horrible too.
They are statistically certain to exist in most of these spaces. There will be abuse survivors trying to cope while others yell at them for being transphobic. They might not have the courage to even say why they cant cope.
If you think this is anecdote, just look at stats, though not every girl is affected the same. Sometimes stats use rape, attempted rape, or other types of assault. Some abuse is way worse than others and I'm not going into it. She can look for herself to see. There may be 6 in the room, and there may be none and they will have reactions unique to themselves.
These spaces are important to them and some girls are frankly not going to handle a male body in their changing space very well. If it is a family member abusing them, this may be the only safe space they know.
The reaction may depend on the personality of that trans person though, perhaps if they were friends beforehand, and how caring and connected the male-bodied person is or can appreciate the reality of those issues to offer appropriate consideration of the girl's absolute need to feel safe there. Many of the other girls also won't know. At this age it is pretty secret and often shameful so they may say different reasons for their actions to not want to be in that space. Even adult women do this. Shame lasts a long time.
Hopefully it is just simple ignorance on the topic.
Maybe she will read a bit about it and find out more about girl's lives.
They are all things that are ALREADY happening.
Paranoid and delusional fantasies, eh?
