Authorities haven't identified the woman but customers at the store in Garland tell Dallas TV station WFAA she lived nearby and had worked there more than a decade.
She was able to briefly describe her attacker Sunday morning and a 36-year-old man was arrested a short time later after trying to break into some homes.
Officers on patrol spotted the fire inside the store and pulled up just as the woman, engulfed in flames, staggered outside. Police put out the flames. She's been unable to speak with authorities because of her injuries.