What should the questioner do to atone for taking some clothes for herself from clothes sent to another orphaned relative, given her inability to inform the sender due to shyness?

Betraying the trust regarding an orphan's property is among the major sins, and its gravity increases, due to the Almighty's saying: "Indeed, those who devour the property of orphans unjustly are only consuming into their bellies fire. And they will be a-blaze in a blazing fire." The duty is to perform sincere repentance and to restore the rights to their rightful owners, whether directly or indirectly.