Holika was burned due to Vishnu's intervention. Holika was given the ability to withstand fire but she never used it to harm others. Holika was truly a good person, and she burnt as her cloth covered Prahlad due to Lord Vishnu’s intervention. Holika is worshipped on Holi because she is believed to be created to ward off all the fears and evil powers. The day is celebrated to signify the victory of good over evil. Holika was called to burn Prahlad as she had the boon of not burning on fire, but due to the devotion of Prahalad, she was burnt and Prahalad came out of the fire alive.