Shemeans that they are hurting Vasilisa unintentionally, such as a human might accidentally step on an ant, or a bear crushes a beetle. Of course we don't know that the ant is there, and the bear doesn't know the beetle is there either, so he wouldn't hate it. He just accidentally hurt it/killed it.
One is like an impersonal pronoun, can be used for people or as an indefinite pronoun. Instead of saying stamps again, they use "one" to replace it. Hope that helps.
