'Inquisitive' has a positive connotation. It means that someone likes to find out the truth or search for answers. 'Nosy' has a negative connotation. It means that a person is too interested in other people's private lives. A 'blabber' or 'loudmouth' can be someone who tells others' secrets. 'Loudmouth' can also be someone who boasts or brags too much, or who uses a loud voice or other overt and rude methods to get attention in an argument.