Depends whether you want a clout round the ear.
chatterbox
Such a person is called a chatterbox.
loquacious
Tu hermana menor habla mucho en el teléfono.
A proper term would be "loquacious" (talkative, garrulous, verbose). Slang terms include "chatter box," babbler, or "motormouth."
what do you call a person who talks very less
Princeton, But When He Talks On Interviews He Can Get Romantic
Professional Poker player. I think he won 2 bracelets in the World series of poker. He talks a lot and wears sunglasses. His sister is also a Professional poker player.
you call her your daughter's husband's sister
You don't call your brother's sister your aunt. Your brother's sister is your sister, or you. Your aunt is the sister of your mother or father.
You would call your sister's daughter your niece.
You would call your mother's sister an aunt.