I am a historian and I work with cultural heritage in Latvia. On 23.of March 2012 I bought a book in one Riga antique (Schillers sämtkiche Werke. Dreizehnter Band, Gottasche Bibliotek: Stuttgart) with an interesting signature : A.Baronin Budberg geb. Gräfin Anrep Elmpt. And on another page there is a registration that this book once belonged to library of family Böninghausen Budberg in Magnushof (by Riga).
Could that be your greatgrandmother, who owned this book?