Gaslighting is a form of mental manipulation. It is an attempt to gain power over another person by causing them to question reality. In Disney movies, this is a common tool among many villains.
Mother Gothel has to be one of the best on-screen examples of gaslighting, she is constantly lying to Rapunzel, telling her she's worthless, telling her she can't do things, belittling her, making her feel less than like she'll never be able to survive outside. Her whole strategy is to get Rapunzel to question her sanity, reason, and judgment. Scroll down to see a few examples of good, old-fashioned gaslighting as demonstrated by Disney villains.