Scottish.  Like the male name, Fraser [q.v.], this use is derived from the surname.

A correspondent [GCB] has noted the use of Fraser for a relict in the Poorhouse records of Aberdeen in 1800 and for a widow in the 1841 Census.  These records for the county show that about a quarter of the occurrences are female.  This use of surnames as forenames is typical in many Scottish families.

Note that the abbreviation (Fras) in the 1841 Census of Aberdeenshire was entirely male.