If we were to assume that the child was kidnapped, then the actual question should be "would she still of been kidnapped if the parents were in the Villa/flat?
Then C would be, in any circumstance where you, or others has had something bad or detrimental to you happen because of your own deliberate negligence or inaction, do you expect or feel sympathy for yourself or that person?
Would she still have been kidnapped if they were in the flat? Probably not, though there have been plenty of cases where a kid gets kidnapped with the parents in the same building or nearby. Still, you could apply that line of questioning to any case where a child gets kidnapped, couldn't you? "Would X have been kidnapped if her parents had been keeping a proper eye on her". I'm sure every parent who has been in that situation looks back and thinks they could have done an awful lot more to stop it from happening.
As for the second part, this happened because someone decided to kidnap their child. The blame lies entirely with the guy who made that decision. Did the McCanns make it a hell of a lot easier for the kidnapper? Yes. That doesn't mean the kidnapping was their fault though.
Example: If I get irresponsibly drunk fall over, am I to blame? Yes. If I get irresponsibly drunk and someone mugs me, am I to blame? No, the mugger is. Did I make it easier for him? Obviously. That doesn't change the fact that I got mugged and he's the bastard that did it.
Sympathy isn't dependent on someone being in the right either though. I probably
would have sympathy for you if you lost your job, house and car, that's pretty damn rough. That doesn't mean I'd pretend you acted like an amazing employee either though. You can criticise someone's actions
and feel sympathy for the heavy price they paid.