Why does Hester return to New England?

By boat!

Why does she return?

Why does she return?

For good or bad New England constitutes her adult roots. More importantly it is where she brought up her precious Pearl. It is the place of her penance and her salvation (eventual public love of Dimmesdale).

She returns to both face her past and resume her life. When she goes back to Boston, she wears the scarlet letter and resumes her work with charity. She's come full circle so to speak.