noun, noun which may take the genitive case particle 'no'
big-sisterly disposition; natural inclination to look after others
Describes a woman who is caring, dependable, and takes on a protective, older-sister-like role toward others, often in social or workplace settings.
彼女は姉御肌で、後輩の面倒をよく見ている。
She has a big-sisterly disposition and often looks after her juniors.
あの人は姉御肌だから、みんなに頼られている。
That person has a caring, older-sister nature, so everyone relies on her.
Compound of 姉御 (あねご, 'elder sister' with an honorific/polite suffix) and 肌 (はだ, 'skin' or 'disposition'). The term figuratively refers to a personality type that is like an older sister.