Gaslighting is a manipulative technique that people use to gain control of the other person in relationship. Considered as emotional abuse, it is where a person's reality is questioned, leading to self esteem and confidence issue. In this case, the person who engages in gaslighting, insists that the other person did something which they did not do, dismisses recollection of events, or manipulates situations intended to blame the victim.
Sources:
https://www.britannica.com/topic/gaslighting
https://www.healthline.com/health/gaslighting#signs
https://www.verywellmind.com/is-someone-gaslighting-you-4147470