Is it possible to get Mac OS X 10.7 Lion without having Mac OS X 10.6 Snow Leopard?

I have Mac OS X 10.5.8 of Leopard. My sister's computer has Snow Leopard, so if i buy Lion on her computer, then copy the files onto a flashdrive or put it on a CD, would that work? Also, if i downloaded a torrent of Lion onto my mac (10.5.8), could i upgrade to Lion from Leopard?