Kororo, although she is not directly a robot (in fact it is a "spiritual being"), in her giantess form acquires characteristics that can make it pass for mecha.
Morphine is originally a fairy, but when she takes her GTS form, she becomes a mecha (despite not being made of metal, but of "spiritual material"), this is rather by its appearance (robotic appearance).
Q·Ko is the protagonist of Q·Ko-chan: The Earth Invader Girl. She is a mecha that can shrink herself to the size of a human girl. Her aspect as mecha has remarkable female characteristics.
The problem is that, despite having a feminine aspect, the metal composition and its robotic aspect take away some of its "human essence" (whatever that means), so some members of the GTS community don't consider female mechas as GTS theme.
Do you consider that female mechas are part of the GTS theme?