She told us not to tell cps.
Could you give examples of what you are not supposed to tell?
Well, she didn't want us to know that she neglected her kids.
It's not good to keep secrets that involve harm to yourself or harm to others. You should talk to someone that you trust about harmful things that are happening.
You make it sound scary. Why should I tell?
You should tell CPS that she neglects her children. Children who are neglected usually do poorly in life later on. Helping them now is saving their lives in the future.