When do you do or say something?

When it concerns children? I came right out, finally, and told my youngest full sister that she leaves her children too much. Our mom has them every weekend so my sister can travel to different places to either visit a boyfriend, or do some modeling job that she never gets paid for, or to just get away. She texted me that if she wanted my opinion she would have asked for it. It makes me wonder if someone like me has any responsibility to try and set things straight. If I believe her children are suffering, or that our mother is being worn out, or that she is being irresponsible by spending what little money she has on car gas instead of living expenses like phone, car loan, rent. And it's not like I woke up this morning and decided today was the day to add more stress to my sisters life. She complained about our mother a little and I felt I had to say something. It's more complicated than that, her children's father is in prison and our mother isn't able to allow my sister to move on.
Another, worse situation; My niece who's mother drinks called me a couple weeks ago to please come get her. It was late and I drove right over. When I got there the 5 month old was screaming and my niece said "please come talk to my mom, she dropped the baby". I went upstairs to my sister and the baby. They were both hysterical. I spoke very softly to them both, gently took the baby and walked him around the house whispering to him until he calmed down. Sister could not calm down. She had fought with my niece, her teenage daughter, and in the process dropped the baby on the tile bathroom floor face first according to my 5 year old niece. My sister cried hysterically over and over that "she pulled my HAIR!" I took the baby upstairs to the teenagers room and quietly asked if her mother had been drinking. My niece believed she had. My sister came into the room and with an ugly snarl asked what we were talking about. I boldly told her, "Your drinking". She snarled at me to give her the baby. Some awful, protective instinct made me say, "If you take this baby I will call Child Protective Services" I'm embarrassed. I let her take her baby and I dialed the CPS # that I already had saved in my contacts. He and the police came right over. They talked with her for a long time and again (I had called them once before but she didn't know it) didn't think there was too much out of place. I made my niece come down and talk with them and show them her bloody hand. They finally gave my sister a breathalizer test and she was very intoxicated. Much more than the "one" drink she said she had. She now has a file on her. The CPS agent wants to help her. She does have a problem and she refuses to believe it. When she is not drinking she is a very good mother. These 2 sisters drive me insane. I blame it on the impoverished childhood and their extreme lack of education. When is it my business? Am I out of line?

Quit taking the Bible out of context.