I don't know what else to do please help!!

Dom💕

my nieces on my SO's side have a HORRIBLE case of lice and have had it for well over a year now. their mom knows about it (and has lice as well) and has kinda tried to get rid of them by lice treatments but has gave up because they just keep coming back. and idk what to do to help them. every time we come around them I try to get the most I can out (without their mom noticing). but obviously im only one person and I know for a fact they have a lice infestation in their house. but they just wont do anything about it. and my SIL is one of those people that gets offended very easily so you can't tell her anything without her getting mad and blowing it way out of proportion. the one person who was able to talk to my SIL and be 100% honest with her was her mom and unfortunately she has recently passed. I want to call CPS and report her but I don't want her to find out and be pissed off at me. I want to suggest to her that she should throw out ALL her furniture and call an exterminator to professionally get rid of them and do multiple treatments on her daughter's hair but I know she'll take that very offensively. I just don't know what else to do. I love these girls to death and hate seeing them going at their hair like they do every time im around. Just so everyone understands how bad they have it the lice is so bad in their hair that you can see the lice crawling around in their hair while they are a couple feet in front of them. I understand how they feel because i had lice when i was younger and it was very horrible and uncomfortable. I was waiting for their babysitter to say something about the lice to her but she still hasn't. Everyone knows they have it really bad but no one has the balls to say anything to her because she gets that offended about stupid shit. I honestly fear that they might need to shave off all their hair just so they can get rid of the lice on their head. Im sorry this is all over the place I just don't know what else to do. Should I call CPS? and if you suggest that I call CPS what will they do exactly?