Yes, GUEST is right, it was Beverley Martyn (nee Kutner). She did record several other things, including of course the albums with John Martyn. In 1966 she made a single on the UK Deram label (I think it was the first release on that label) "Happy New Year", which included Jimmy Page among the session musicians (hence the single is souight after by collectors).

See here for more info.