Hmmm.....from past experience, I think this is going toward one of the common dodges, which is a slight variation of dodge 1 mentioned previously. However, I'll try not to jump to that conclusion and just answer the question seriously.
First, girls who "sexualize the context".
I don't know what's going on in their heads, so they might very well be sexualizing the context. If they make no overt display of sexualizing the context, I would never know. People who make an overt display of sexualizing the context would be restricted.
Second "Girls who fail to respect the modesty of others using the space."
I'm having a hard time understanding the question. If you use a girls' locker room, there is an expectation that people will see you fully or partially disrobed. That might violate your sense of modesty, but if all of those people who see a girl disrobed are, themselves, girls, the girl whose modesty is offended in that situation would not have recourse to fix the problem. It's normal. It's expected. The other girls, the ones who are not respecting the modesty of the shy girl, are still allowed to use the locker room. So, yes.
In short, in the normal use of locker rooms, girls who use the locker room do not overtly sexualize that use, but they do see each other fully or partially disrobed, which might offend someone's sense of modesty. Girls who overtly sexualize the use of the locker rooms will likely be prohibited from future use. However, girls who "fail to respect the modesty" of other girls are not excluded. Lack of modesty in same sex situations is expected. That's why we have two locker rooms.
Now, you asked about girls. By "girls", I mean the concave variety of human. If you asked about the convex sort of human, I would answer differently.
I was asking you about convex sorts who, despite their convexity, feel that they ought to be allowed to use the girls' locker room. Do you think that should be allowed?
(If your answer goes beyond "yes" or "no", feel free to use anything in my answer about girls as part of your explanation, if that is useful.)