I think by the ending she already did grow up. Since it's a little open ended one can't easily presume who she ends up with, but I think she's hinted to be ending up with Yui.
Just a hint, considering how both of them are acting. Well, at least her mother's all better now. She's not particularly gay - she doesn't seem to have a preference for genders. She's just really scared of men, and that's the whole issue of what she's trying to deal with here.
Now that she's taking steps away from that fear and learning to move forward "tge clothes in the past don't fit me anymore" aka. She has a broader world now. To phrase it simply, it wouldn't be pleasant to see her end up with girls because she's scared of men, rifht? It's a lot nicer if she ends up with who she falls in live with whether or not the person is a girl or boy.
Please grow up and find a nice girl who will support and like you for who you are. I will imagine you graduating and dating beautiful princesses in college. I also hope your mother gets over her damn self and that Yui isn't too heartbroken when he figures out that you really are gay.
All the best,
XOXO
P.S. Tokyo issues same-sex partnership certificates as of 2015.