I wanna say 'OMG' but I have seen such before...
I agree with moshe... police escort for retrieval and video documentation
Also go ahead and get the social workers involved if you can since this might call into question the fitness of them to parent her half-siblings (or create documentation for when they get kicked out in a few years)
Speak to your lawyer too about obtaining full custody of your daughter under these circumstances
Have your daughter write out her account of what was said and what is happening (including her emotional feelings about all of it).....again documentation
Such documentation is valuable for you, her and later down the line for her half siblings because they will certainly be in a bind themselves in a few years and she could provide their social worker with such evidence of abuse/neglect and emotional trauma.