If a person of the male sex is in a space designated for people of the female sex, that space is no longer a same sex space, is it? Sex is not the same thing as gender, as even trans activists are fond of saying, though they fail to apply this fact logically.
So the question we should be asking, which has been asked and answered on here a thousand times already, is are unisex spaces more dangerous for women and girls than single sex spaces? Yes, they are.
It is barely relevant whether an individual transwoman has or ever would harass or attack a woman in a female single sex space. Simply by entering the space that person is breaking down the boundaries that keep women safe, directly contributing to a culture that says that women do not have the right to single sex spaces. Any transwoman who had any respect for women would realise that those boundaries are really important and saying 'Oh, you can let me in, I'm no threat' may be completely true, but it nevertheless chips away at those boundaries and endangers women indirectly. You can be the nicest person in the world to women that you meet in person but if you don't respect sex segregation you are still working to erode important women's rights. It's so incredibly selfish and egotistical to think otherwise.