As far as I can recall, she was supposed to have been launched from Earth in 1996. As in, a ground launch. I think that's how I've always taken it to be.
Which I guess means she was built on Earth as well.
'If the Apocalypse starts, beep me!' - Buffy Summers
'The sky's the limit.....' Jean-Luc Picard, 'All Good Things'
courtesy of Saquist