I'm sorry but you are ignoring the GNC women, some of whom are on this very thread, who say they understand this is happening as a result of trans women pushing female people's boundaries and would rather be challenged themselves than have women afraid to challenge anyone.
And I'm very sorry that the entitlement of trans women, encouraged by genderist activism, has lead to the point where there is no pain free solution. This did not have to happen. There are many ways society could accommodate trans women and it's a real shame that gender ideology insists - well, let's not mince words, lies - that the only option is to appropriate female spaces, resources and emotional safety in service of males. But, given this is where gender activists have chosen to take us, I would rather some female people are unfortunately embarrassed than all female people are made less safe and less confident in order to meet demands of males.
You worry that even a young ‘tomboy’ girl should be raised to handle being confronted by an angry adult in the toilets (you didn't mention this but let's be clear, this wouid specifically be an angry female adult) but apparently aren't worried that the alternative is that young girls will need to be raised to face an angry or over friendly male adult in the toilets instead.
Incidentally, if you are OK for women's toilets to be open to trans women but not other males, who exactly are you expecting to challenge the men who should not be there, and how is that any different to this scenario?
You accuse feminists of turning GNC women into cannon fodder based on the risk they may be challenged, but you want to turn all female people into cannon fodder with a risk of much worse simply to accomodate male demand.