2007 Dodge Caliber Starter

I was driving when all of a sudden my starter started cranking making a huge noise in the motor. I pulled over and pulled the keys out of the ignition and it was still cranking all by itself. This is a problem that has occurred about 8 times total. The first time it happened, I fried my starter because it happened on the highway. My girlfriend is starting a new job on Monday, and I have zero confidence in her taking the car back and forth to work. Please help.