I think there are people who are less combative, less likely to stand up for themselves and so become a lightening rod for dysfunction.

In fairness though they have just as much responsibility to deal with the situation as those who are treating them poorly. These situations are rarely one sided. That said i think someone can only be taken advantage of for so long - there has to be the hope that a situation will positively resolve itself before it gets to this point.

Just keep getting the appropriate help for yourself so that in the very least, you'll know that you're not contributing further to the problem.