Here's the thing LEM (at least from my POV), Girl Guides is a girl's only organisation. Parents (some) send their children there for that reason, some girls go there rather than scouts for that reason.
If a natal boy decides to identify as a girl and attend guides and other parents don't know he is there, sharing close spaces and sleeping that is completely unfair.
If parents want to send their children to scouts which is mixed and may have mixed sleeping accommodation (my DS didn't go to the mixed sleep camp as we were away however there were a million safeguarding forms apparently but he went to the camp where the sexes were separated for sleeping etc) then they get to make that choice.
Teenagers like to have sex, I know when I was a teenager I went to quite some lengths to have sex when I shouldn't as did a lot of my peers be they make or female. When I went on school trips teachers patrolled the halls because the hotels and hostels required them to do so simply because their experience of housing young people shows them that teens with the opposite sex organs like to use them.
Teenagers now spending a weekend close to each other, bonding and now sharing s room as "girls" when one (or more) of them has a penis?
How long until they are having sex or a girl ends up pregnant?