When the monster was killed by Hermes she put hundred eyes onto peacocks feathers?

The monster you are referring to is Argus Panoptes, a many-eyed giant in Greek mythology who was killed by Hermes on the orders of Zeus. However, it was Hera, not Hermes, who placed Argus' eyes onto the tails of peacocks as a way to honor and remember him. So it was Hera, not Hermes, who did place the hundred eyes onto peacocks' feathers.