CLKD, luckily not. Even saying that makes me feel bad! I have my own kids and am quite a caring, maternal person really. Two of the step-children are fine, it's just the eldest.
If I don't interact much with her my husband thinks I'm being 'off' even though he knows how difficult she can be. He's a typical male, always trying to find a solution and trying to convince me that it'll be fine even though I know it really won't be and I'll struggle to get through the day without losing it with someone (most likely him). My tolerance levels are really low these days.