How bad is it? It's an unfunny self-parody by a poor director.
Should you see it? Only if you watched Bloodrayne: Third Reich and actually liked it.
Uwe Boll has been called by some the worst director since Ed Wood, Jr., but that isn't fair; his films are usually saddled by bad scripts originating from video games - but that doesn't make them any better. I've never played BloodRayne, so I can't comment on authenticity, but Boll's directed three films in the BloodRayne series and during the third one, simultaneously filmed this parody of his own work. Unfortunately, most of the humor is sophomoric and insulting. Blubberella is half-vampire and fights Nazis while eating a lot, but accidentally makes Hitler immortal, making her the only one who can stop him and his undead army. Clint Howard makes an appearance, which is always a nice touch, and Boll himself plays Hitler.