CPS may NOT the BEST choice at this point; because if she's an able-bodied adult (physically ABLE to work, or physically ABLE to leave, yet hasn't), but is keeping the children in a home where they are starving, she DOES risk the children being removed from the home. She REALLY needs to be working with a local domestic violence advocate who can help her to start to secure more control over her life, get the divorce moving, and to help DOCUMENT the situation as part of a number of possible approaches to getting herself and her children into a better situation, as Doggie noted via things like custody orders, alimoney orders, child support orders, restraining orders, etc..
In CA she can call 800-524-4765 to be put in touch with local resources who can assist her. If it takes her leaving with the kids and going into hiding in a shelter for a time, then that's what it might take. But if the situation is as dire as you project, then she needs to either get the kids OUT of the situation, or potentially risk an outside force taking them out of it.

