What do independent directors of a company like Swiggy do ? How are they rewarded for what they do ?

Ideally they are supposed to look out for the small shareholders and keep things ethical as overseers. But more realistically they are a regulatory requirement and lend credibility to the company and management. They get paid salaries and sitting fees. For listed companies you can check how much directors got paid in their annual reports.

I think she lost faith cus the company was not transparent with its numbers to her.

The quid pro quo here is brand association.