Would you be offended by this?

I have 2 small children (5 and 4 months) my in-laws recently became foster parents and hope to eventually adopt. The child that they are going to be fostering (possibly adopting) is 16 and has been severly phisically and ually abused... she even tried to do things to her brother.... now my problem is why would my in laws subject my children to someone like this? I know it's not the girls fault that is was done to her and i do feel bad for her but at the same time i don't want my children around that. They also have 3 other grandchildren other than my 2. My oldest likes to spend the night there and my husband and i have discussed it and when she gets to my in laws it won't be happening anymore.. they are offended by this and think that if they give her a good home and get her the help she needs, they can change her... i don't think so. What do you think?