Well, if Ahsoka were on Earth in a fanfic, she'd likely have a hard time adjusting at first. The different cultures and technologies would be quite a shock. But she'd soon start using her Force abilities in unique ways. Maybe she'd use the Force to help with environmental issues, like cleaning up polluted areas. She could also sense the emotions of people around her and use that knowledge to try and bring peace in conflict zones.
She might be a strange and powerful figure. People would be both in awe and afraid. She could use her lightsaber skills to fight against Earth's bad guys, like a super hero.