Please Help I need advice about teen neglect

My “step” niece is 14 and my daughter is 15. They have always been very close and really have a special relationship. They loved to act kind of wild, having sleepovers with bags of candy to get hyped up and playing loud music – just innocent kid stuff. They don’t go to the same school, but are connected by their phones, of course, so they have continued to be close. My daughter has always had anxiety and been through some other serious issues that we continue to work on, but our communication is really good. We keep a close eye on her and monitor her online activity regularly, while still letting her have freedom. She is doing so much better!
I am worried that her cousin is really having some problems and her online activity is clearly not being monitored; actually, she is not really being watched much at all by her parents. She posts pictures with drugs, sexual content and just overall bad stuff. Her parents are divorced and both have drug and mental health issues. She also has learning disabilities and is 3yrs behind in most subjects. Her mom is remarried to a nice guy, and when she is with them, things are sort of okay, although her mom has always had parenting judgement that I don’t agree with. The Mom wants to be her daughter’s friend, more than her mom. She took a bunch of pills a couple months ago and went to the ER and then to a facility for a week after this suicide attempt, but nothing about her home life has changed. Her dad (my spouse’s brother) has been taking steroids for a few years and he has anger issues, along with chronic depression. He used to be in construction but now grows and sells weed. He is never home when the kids are there, and usually there isn't much food and they are pretty much on their own. There is also a 16 yr old boy who helps dad on the pot farm – he went to the hospital for alcohol poisoning in the last year. Both parents do not supervise the kids (never did) and the girl cousin posts stuff about being out at 1 or 2am partying and wondering around without answering to anyone. My spouse’s family “sort of” talks about it, but most of them are in denial and just keep trying to fill in for the kids where they can. The guilt I am feeling over knowing what a bad situation this is, is getting bigger and bigger. My spouse has mentioned called CPS as something they would never do because it would be even worse for the kids. I feel like that is probably true, but I don’t know what to do. The postings online are almost more disturbing now than they were before.
What can I do? If I called CPS and anyone found out or suspected it was me, it would be horrific, to say the least.
What can I or should I do? Before something even worse happens???
Thanks for reading this.

Your concerns about your niece are certainly valid. It does sound like there is a lack of supervision and role-modeling in this girl's home.

What about calling the CPS hotline and line out what you are seeing to the caseworker without giving names and see what they recommend before making an actual report?

Maybe the best thing you have to offer your niece is a solid, loving environment she can visit and an adult she can trust if she needs someone to turn to.