The Collaborative International Dictionary
By herself
Herself \Her*self"\, pron.
An emphasized form of the third person feminine pronoun; -- used as a subject with she; as, she herself will bear the blame; also used alone in the predicate, either in the nominative or objective case; as, it is herself; she blames herself.
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Her own proper, true, or real character; hence, her right, or sane, mind; as, the woman was deranged, but she is now herself again; she has come to herself.
By herself, alone; apart; unaccompanied.