First I need to ask if she has been spayed, as some dogs have weak bladders from spaying, the next question is she closest to your son, if so she is marking her territory on him to make sure other animals in your house know he's his.
You are doing the right thing by stopping her doing this, however to bring confidence into her life it might be a good idea to clicker/treat train her for positive re-actions, this method helped with one of my dogs I brought in plus she's been trained for agility which she adores, I always carry treats around with me incase she spooks at anyone, I give them the treat to reward her and click so she knows I'm pleased with what she's doing, hope this helps, it's never easy having a nervous dog especially a BC.
Sue xxx