Cocktails 1 & 2 - probably one of the more vile series around, directed by Lizzy Borden.
S.I.D.S 1 & 2 - another series from Lizzy.
Forced Entry - Lizzy's latest: "A Stunningly Disturbing Look At A Serial Killer, Satanic Rituals, And The Depths Of Human Depravity." I haven't seen it (and don't plan to) but I think it speaks for itself.
In the Days of Whore - One of Thomas Zupko's best offerings...lots of rough stuff in this one, but not quite as stomach churning as some of the stuff in Cocktails 2 .
Extreme Porno Boot Camp - not really "sick" but an interesting porno meets reality TV experiment where six new "recruits" compete for a contract.
On the other side of the coin, I'd recommend "initiating" your girlfriend with some Andrew Blake stuff. Night Trips might be a good choice. It's still hardcore, but there's much more to appreciate than the rudimentary mechanics of the performances. Plus it can be purchased relatively cheap on DVD...but Caballero's transfers suck.
Films with plots are being made. They're often referred to as "Features" and you'll find them from studios like VCA, Vivid, Wicked, and Metro. Like any genre, some are good and some are bad. Check out the reviews on this site for more info.
Hope that helps.
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