Short answer - Yes, I believe there is no problem with me being near your DGD in a changing room
Here is my problem with this. My DH is safe around children. He’d be mortified to find himself in a changing room full of women but he’d be no danger (probably be apologising profusely and looking the other way in great embarrassment whilst running for the door.) he is no danger to women or children.
But he still shouldn’t be in a women’s changing room, because it’s not OK for any male bodied person to be in a women’s changing room. So while he, personally, is no danger to anyone, he’d never even dream of accessing such an area. Because he understands that its not about him. he understands that its about women and girls’ safety in the presence of men as a class.
This is not about individuals. For an individual to say ‘well do you think I’m unsafe? That’s offensive to me, I demand in’ is not the point. The point is that we have sex segregated spaces because women and children as a class are vulnerable to men as a class.
The safety, or non safety, of any individual of small group of individuals is irrelevant. What’s relevant is the class protection remains.
Back to the OP: What’s relevant in terms of sexual orientation is that that orientation isn’t personal - a lesbian HAS to have the right to exclude all males as a class. Inconvenience or distress or offence to an individual is neither here nor there.