Supporr needed

Hello all, i am very new to all this and am in need of support please. Me and my sister are fostering my 4 nephews. Their mother has been doing video calls with the older boy and keeps telling him to not trust the social worker that she is trained to lie and it is really messing with his head. And is also making comments about wanting to see all of the stuff in our house. Ive told the social worker on a few occasions about this and she said to stop doing the calls. Then after the boys and their mom had their first visit the social worker changed her mind and said the calls could happen. Idk what changed i just know the mother is a very good lier and manipulator. I am NOT ok with the way the calls have been going due to the manipulation or the fact that they are on video. She only calls at 8pm never earlier. Idk my rights with this or how to talk to the social worker about my concerns. The oldest boy is 6 and the younger 3 are not old enough to know what is being said on the phone. Oh and also i just found out the mom is pregnant with another baby. Thank you