PROTECT THE CHILDHOOD FRIEND ROUTE!!!
Seriously, childhood friend is the best route and I like this author for pulling it through even if it was some side character just for a joke.
Whenever I start reading something new I always like trying to think up a bunch of different ways the flow of the story could go and see if one is right. So I'll just put them here
First path, the gyaru will think it is weird and start to distance herself which I don't really see happening because she seems like she will be a consistent character going forward.
Next path, the gyaru will talk about it casually and the other students at the school will end up causing other students to avoid her because in their own eyes they aren't lesbians and her seeing them as such disgusts them. (this one also seems unlikely for the tone of the story so far)
Another path, the gyaru keeps quiet and it becomes a secret between the two as they watch the yuri form around them, all the while the gyaru is giving the MC hints that she likes her that never get noticed. (this is the most predictable and likely I think)
Last I'm gonna put here is that it could get out that she likes yuri and then it ends up that there are a lot of other students that are yuri/yaoi otaku too and such characters will expand the main roster of characters. (probably not)