She may have been the first to use it for vampires (though with the extensive vamp lit writings I'd be surprised of that), but it's a pretty common word. Any dictionary will give you a few similar uses, like siring of beasts, or sire as maker, etc.
Oh, except that normally a sire is a man. For vamps you can have a woman be a sire, which is a use of the word you definitely won't likely find anywhere else.
