First off posting annonymously because im not sure if who im going to talk about has one of these. I need advice. So please help and no rude comments

So first off im 19 and i have a son... i have a friend who is 20 and has a son too (hes 15 months). Lets say this friends name is mary....

Mary stays with me and my parents. When its bedtime mary gets her son to sleep... but then he will wake up crying... and screaming. I tell her to do something because she will just LET him cry. She wont do anything unless i tell her to help him. She will then try to tell him to go back to bed... she gets super frustrated when he doesnt go back to bed as soon as she says that. She will start cussing at him. Start to russle around with him.. and by that i mean grabbing him and laying him back down over and over again and every time she does that he screams so im thinking she does it pretty hard.. shes been sleeping on the couch with her son. She will be at one end of the couch and literally throw him down on the other side of the couch... then he really starts to cry and shes just asking him to stop crying... i try to tell her to rock him stand up with him pat his butt, i try to give her advice and i have my own kid to worry about... but i feel so bad for this baby, that i took over a couple times, as soon as i would pick him up and just gentally talk to him he calmed down.... all she wants to do is sleep, she doesnt care what she has to do she is gonna sleep. She will just ignore him and go back to sleep... which is rude not only for the son but for my family as well because we want to sleep too...and her son SCREAMS loud and will not stop till you calm him down.

Ive tried helping her like giving her advice on what to do to get him back to sleep but she just gets mad at me and ignores me. I want to say something. I want to say that she cant just be throwing him around like that because he can really get hurt. He can hit the edge of the couch with his head or bounce off the couch and then she will feel really bad.... i do not like her parenting style AT ALL and honestly think she needs to take a parenting class. Or take some of my advice... but heres my problem, you know how moms dont like getting told how to take care of their babies? I mean i know i dont, i rather do it myself. Well im just scared she would get mad at me and think im trying to tell her what to do. She literally does this shit everynight. And its getting really old. I cant take it anymore. She needs to change and change quick. Me and her are TOTALLY different as parents and its just not okay to act that way towards your babies... I need to say something in a way it doesnt sound like im telling her what to do so she doesnt get the wrong idea..... or maybe i should ? Im not sure.. i really need help on this. Im tired of taking over and taking care of HER kid. Most of the time i feel like im a mom of 3. Mom to my son, to her son and to HER. (Im always telling her to feed her son, to clean her cats liter box, to clean up her mess etc)

Anyways i think you get the point. She gets frustrated way to easily and gets agreesive with her son. So i need help. What would you do or say? Thanks.

How would i call cps on her? She would know it was me, because no one else would know how she takes care of him except for me and my parents.

My mom says she needs to start being a better parent. My dad says he feels bad for that baby because she never watches him she lets him do whatever until i tell her to get him or see what hes doing. My dad wants to call cps but hasnt yet