Issue with bf ex gf, she is crazy wondering if she will harm the kids?

now some of what she get mad about i can understand, but here what been going on if he don't come to visit she get really pissed and starts on everyone in his life, i told her it was not my fault if we don't come up to get the kids and she says she knows this but last time we did not come when he said he would she called me names his mom names and his other daughter names and she is only 15 yrs old, a preacher molested her and she said it was her fault she was a ho, and yes she wants him back, she told him this, she kicked him out 9yrs ago on xmas and newyears eve moved a man in and she could not even speak his language she had to learn it, she has told my bf she was having him watched so that was one reason we move 130 miles away from her, now because of how she is acting he is worried as well as his family that she may hurt the kids, if he don't pick up the phone she will call 30 times or more in a day if he answers a text she will text just as much as she will call, cussing every one out, 3 times i said i would not go to pick those kids up and then a few months later i did take him to get them he can not drive, his parents have already said they would wait until those kids are 18 to see them, if he call the kids he must talk with her first and then after wards she will put the kids on put on speaker phone only, do you think she is capable of harming those kids, and yes i know it is not my place and by not going to pick them up it take me out of it at least i hope so,