Half of the obvious answer would be that Sauron only tortured elves to make them in the beginning, & the other half would be that Sauron bred them using his power, I'm sure he didn't need an 'help'. But some really interesting opinions have probably been brought up in one or all of the threads that
Eomer mentioned, so try there...
p.s. i love the way we're calling them she orcs, i guess the 'she elf' trend that the movies started has caught on
.